A terror suspect arrested after a car crashed into a barrier at the Houses of Parliament at high speed is not believed to be known to the security services, police have said.At least three people were injured when the silver Ford Fiesta hit a group of cyclists and pedestrians waiting for traffic lights to change. Rooftop camera footage shows the car mounting a pavement on the wrong side of the road before, witnesses said, it travelled at up to 50mph for around 40 metres (130ft) and hit a bollard.Scotland Yard said a man in his late 20s was arrested after the incident at around 7.30am on Tuesday. The suspect was taken to a south London police station, where he remains on suspicion of terrorism offences. He is not co-operating with officers.Meanwhile, as Theresa May warned of the “severe” threat facing Britain, new figures showed a sharp rise in terrorism investigations, with the number of live cases of suspected plots rising from more than 500 in March to 676 by the end of June.The Met’s counter-terrorism command is leading the investigation into the latest attack. Officers are seeking to formally identify the suspect, but “don’t believe this person is known to either MI5 or counter-terrorism police”.The suspect is reported to be from the Midlands and it is believed that he might have travelled to London from Birmingham. Metropolitan Police statement as man arrestedThe man arrested over the Westminster car crash is in his 20s and is being held on suspicion of terrorist offences, Scotland Yard said. It said in a statement: “At 07:37hrs on Tuesday 14 August, a silver Ford Fiesta collided with a number of cyclists and pedestrians, before crashing into barriers outside the Houses of Parliament.”The driver of the car, a man in his late 20s, was arrested at the scene by armed officers. He has been taken to a south London police station where he remains in police custody.”He was arrested on suspicion of terrorist offences.”There was nobody else in the vehicle, which remains at the scene and is being searched. No weapons have been recovered at this stage.” Defence Minister Tobias Ellwood, who was branded a hero after stepping in to help emergency services in the wake of the 2017 attack outside Parliament, said today’s incident was a “stark reminder of the threats we continue to face”. He wrote on Twitter: 11:54AMPolice ‘don’t believe suspect is known to counter-terror officers or MI5’ 2:05PMUS ambassador: America’s prayers are with all the innocent people hurt Scotland Yard said in a new statement: “At 07:37hrs on Tuesday 14 August, a silver Ford Fiesta collided with a number of cyclists and pedestrians, before crashing into barriers outside the Houses of Parliament.”The driver of the car, a man in his late 20s, was arrested at the scene by armed officers. He has been taken to a south London police station where he remains in police custody.”He was arrested on suspicion of terrorist offences. There was nobody else in the vehicle, which remains at the scene and is being searched. No weapons have been recovered at this stage.” Witness Kirsty Moseley, 31, was sitting in a car behind the cyclists at the traffic lights.She said: “The first thing we noticed was his car driving at high speed into the cyclists. Then he went straight through them and rather than continuing and hitting us he swerved and went over the central reservation. “The cyclists were scattered everywhere and then we just heard this huge bang. That’s when we looked round and he had driven into the barriers. One cyclist got up and started screaming at him to come back. We were all in shock at that point.“There was an ambulance that happened to be driving past at that very moment, so it was there to help the injured within seconds. Then the police were there so quickly and there were so many of them.” The car, circled, drives past Westminster Abbey Armed police surround the driver outside the Houses of ParliamentCredit:ITV supplied by Pixel8000 And a television cameraman who happened to be on the scene described the dramatic moment armed police swooped on the car, reports Patrick Sawer.Donovan Parsons, who was filming for ITN nearby, said: “We saw people running away from the crash and quickly realised it was more than just an accident.“As I got there I saw a silver car smoking against the barrier at the entrance to Westminster Palace and armed police scouting the area.“Then four 4×4 police vehicles turned up and armed cops jumped out and pointed their guns inside the car. They then dragged this guy out and I could see them pointing their guns inside the car. That’s when we got pushed back behind the cordons.”Video: ITN cameraman on what he saw unfold Police recover the car driven by a 29-year-old man who was arrested on suspicion of preparing an act of terror in WestminsterCredit:PA And Vince Cable, leader of the Liberal Democrats, said: “Thank goodness the barriers are in place and worked.” Meanwhile, Westminster Tube station has reopened and the Met Police said: “We are now in the process of removing our wider cordons, thanks for your patience and understanding.”The immediate scene, Abingdon Street, between Parliament Square and Horseferry Road, j/w Lambeth Bridge, will remain cordoned off for some time.” Parliament Square was evacuated as a large number of police cars descended on the heart of Westminster, which has seen heightened security since the Westminster Bridge attack in March 2017. Streets around Parliament Square, Millbank and Victoria Tower Gardens were also cordoned off as dozens of armed police swooped on the scene.A series of ambulances had been sent to the scene and the London Ambulance Service said two people were treated for injuries that are not thought to be serious and taken to hospital. A third person was assessed for minor injuries at the scene.’It looked deliberate… he hit bollard at 50mph’Local businessman Jason Williams was walking to work when he saw the crash unfold.The 45-year-old, from Kennington, south London, said: “He had driven it at speed – more than 40 mph. There was smoke coming out of the car.”He told the BBC Radio 4 Today programme: “I have seen people on the ground, lying on the road. I don’t know if they have actually been hit by the vehicle or not. I saw at least 10 people lying down.”I was told basically to move away, to run. I have run for my life.” The Houses of Parliament are surrounded with security barriers of steel and concrete.The measures were extended in the wake of the Westminster Bridge attack in March 2017, when Khalid Masood ploughed a car into crowds on Westminster Bridge, killing four people.Masood abandoned his car then stabbed and killed unarmed Pc Keith Palmer before he was shot by armed police in a courtyard outside Parliament. Streets around Westminster were cordoned off amid the police operationCredit:Sam Lister /PA A police officer jumps a barrier as the car approaches Terrible events at Westminster. America’s prayers are with all the innocent people hurt this morning. As the investigation continues, one thing is clear: the police, the paramedics, the ambulance drivers – they ALWAYS do this country proud.— Ambassador Johnson (@USAmbUK) August 14, 2018 Scores of commuters on foot and cycling arrived at the police tape trying to get to work.Workers at Portcullis House have been allowed through the extended cordon and were seen queuing to get into the building. Mr Williams told Good Morning Britain: “I saw a car going at high speed towards Parliament. It hit a bollard.”He added: “It looked deliberate. It didn’t look like an accident. How do you do that by accident? It was a loud bang.”Mr Williams added: “He’s obviously gone into the bollard at high speed.”It seemed it was about 40-50mph, there wasn’t any shouting or anything – I’ve seen smoke coming from the vehicle.”He did get out [of the car], I was behind and I did hear a loud bang and I’m seeing what’s going on, but I couldn’t hear if the police asked him to get out. The specialists came soon after, I’d say within 5-9 minutes.”He said the suspect was quiet when he was taken away by the police. 1:40PMFiesta remains near Parliament as forensics officers work at scene A circled aerial image shows where the car ended up after the attackCredit:pixel GRG US President Donald Trump, referring to the Westminster car attack said “these animals are crazy”. Mr Trump wrote on Twitter: 10:37AMPolice treating Westminster car crash as terror attack Meanwhile, witness Ewelina Ochab said the vehicle did not appear to have a front registration plate when it crashed, adding: “The person driving did not go out.”She said: “I think it looked intentional – the car drove at speed and towards the barriers.”I was walking on the other side [of the road]. I heard some noise and someone screamed. I turned around and I saw a silver car driving very fast close to the railings, maybe even on the pavement.””The person driving did not go out” of the vehicle, she said. The remaining patient being treated by medics is at St Mary’s Hospital in Paddington, west London, a spokeswoman for Imperial College Healthcare NHS Trust has said.A statement added: “We can confirm that we have received one patient from this morning’s incident in Westminster Witness Barry Williams said the car had accelerated towards the barrier after hitting the cyclists.”I turned round to see a silver car heading towards the cyclists on the wrong side of the road, they were parked waiting for the lights to change,” he told the BBC’s Victoria Derbyshire programme. “He hit the cyclists then swerved over towards where the safety barrier is…. and accelerated and hit it at quite a high speed.”I wasn’t sure whether he meant to hit the cyclists, they might have just been in the way, but once he did, he accelerated towards the barrier. Assistant Director of Operations Peter Rhodes said: “We were called at 7.40am today (14 August) to reports of an incident on St Margaret Street, SW1. “We sent a number of resources to the scene including three ambulance crews, responders in cars and an incident response officer.”We have treated two people at the scene for injuries that are not believed to be serious and have taken them to hospital.” The force spokesman added: “At this stage, we are treating this as a terrorist incident and the Met’s Counter Terrorism Command is now leading the investigation.”Ambulance service: Three injured people treatedTwo people were treated at the scene in Westminster for injuries that are not thought to be serious, London Ambulance Service said.A third person was assessed for minor injuries but not taken to hospital. 3:28PM’Cyclists were scattered everywhere… then we heard this huge bang’ 2:50PMVideo: Minute-by-minute – how the crash unfolded 1:51PMPolice have stopped 17 terror plots in 18 months A meeting of the Government’s emergency Cobra committee will be held at 2pm to discuss the crash outside Parliament.Meanwhile, we are expected to hear from Metropolitan Police Assistant Commissioner Specialist Operations Neil Basu outside New Scotland Yard shortly. No one else was in the car and police said no weapons had been recovered from the scene.Speaking outside New Scotland Yard, Neil Basu, the Met’s Assistant Commissioner for counter-terrorism, said police and the intelligence services were working to establish if the suspect was part of a wider terror cell and if he had received assistance from others in planning the attack.Mr Basu said: “It appears to have been a deliberate act, but what the motive was we can’t answer at the moment. We haven’t formally identified the suspect, but we don’t believe he’s known to MI5.”He added the attacker was not been pursued by police before he struck the entrance to the Palace of Westminster and that the blue lights seen behind him in footage of the incident were those of an ambulance coincidentally answering a separate emergency call. 2:44PMWestminster council leader: Our democracy, and our way of life, will continue to defy those who try to undermine it A police officer in a forensics suit next to the car used in the attackCredit:HENRY NICHOLLS /Reuters 9:38AMMet’s counter-terror command now leading investigation 1:06PMDonald Trump: Terrorist ‘animals are crazy… and must be dealt with through toughness’ Police forensics officers surround the car where it crashed on Tuesday morningCredit:Victoria Jones /PA Armed police outside St Thomas’s hospital in Westminster after a car crashed into a security barrier in Parliament SquareCredit:Rob Pinney/LNP Armed police point a gun at the male driver as they surround the car outside the Houses of ParliamentCredit:ITV WESTMINSTER INCIDENT:A stark reminder of the threats we continue to face, the need to remain vigilant and the professionalism of @metpoliceuk in once again swiftly and courageously responding to what looks like a crude and deliberate attack on Parliament.#westminster pic.twitter.com/kxNO6Ra3cu— Tobias Ellwood (@Tobias_Ellwood) August 14, 2018 The force spokesman added: “At this stage, we are treating this as a terrorist incident and the Met’s Counter Terrorism Command is now leading the investigation.” He added: “The police were very fast, they vaulted over the safety barrier and headed towards the car.”What also happened was the police started to head away to block off people heading towards us. The cyclists…there was a few on the ground, some were holding their arms, there was bikes everywhere. It was frightening.”Mr Williams added: “There was about 10 cyclists waiting for the lights to change… he hit about four or five – one of the cyclists got up and was about to chase the car.” On the driver, she said: “I saw him drive past. He wasn’t shouting and he just had two hands on the wheel. He was just staring straight ahead. He looked quite sure. He was just peering over the steering wheel. He knew what he was doing and he was focused on what was in front of him rather than being erratic or shouting. “After seeing how he drove into them, we are amazed that only one woman has been seriously injured.”Miss Moseley was on her way to work in Oxford Circus with her husband, Patrick Moseley, 34, from their Brixton home. “We don’t usually drive,” she said. “We usually cycle, but for some reason we decided to drive this morning.” Responding to the attack, Nickie Aiken, the leader of Westminster City Council, said: “Our thoughts are with those hurt and our thanks to the brilliant emergency services who were so quickly at the scene. “The House of Commons was targeted again today – as it was last year – but our democracy, and our way of life, will continue to defy those who try to undermine it.“The safety of the people who live, work and visit in Westminster remains our priority and we will work to ensure our capital remains a welcoming city.” 12:34PMRemaining patient treated at St Mary’s Hospital in Paddington Neil Basu, Assistant Commissioner of the Metropolitan Police and counter-terrorism head, is giving an update outside New Scotland Yard. He has said: One woman is being treated for serious but not life-threatening injuries. Another person has been discharged The arrested man is in his late 20s “Given that this appears to be a deliberate act, the method and the iconic site… this is being treated as a terrorist attack” No other suspects have been identified and there is “no intelligence at this time of further danger” to Londoners or the rest of the UK connected to this incident The vehicle is vehicle is being searched. No weapons have been found Police are seeking to identify the suspect and “his motivation if possible” Mr Basu added that the suspect was not co-operating with police and had not yet been formally identified But on the basis of the information known so far, “we don’t believe this person is known to either MI5 or counter terrorism police,” he added. The man being taken away by armed police was arrested on suspicion of terror offencesCredit:Sky News Armed police in Parliament Square as the heart of Westminster is in lockdownCredit:HANNAH MCKAY /Reuters The terrorist threat against the UK is seen as unprecedented. In addition to five attacks last year, authorities say they have stopped 13 Islamist and four extreme right-wing plots since the Westminster atrocity in March 2017.Police and MI5 are running at least 500 live operations involving roughly 3,000 active “subjects of interest” at any one time – while there is also a wider pool of more than 20,000 individuals who have previously featured in investigations whose threat must be kept under review.Earlier this year, the Government unveiled a refreshed counter-terror strategy. Under the blueprint, MI5 intelligence will be shared with bodies outside the security community in an attempt to stop suspects before attack plots can crystallise, while anti-terror laws are to be strengthened to allow earlier interventions. British Transport Police (BTP) said it would be putting extra officers on patrols in England, Scotland and Wales on Tuesday afternoon and into the evening following the Westminster terror attack.Superintendent Chris Horton from BTP said: “We know incidents such as this are likely to cause concern, so our officers will be highly visible both on board trains and at stations.”We are there to reassure the travelling public, so please don’t be alarmed if you see our officers, including firearms officers, on your journey.” 11:43AMPoliticians praise emergency services for bravery that ‘keeps us safe day in, day out’ Our thoughts are with those who have been injured in the incident outside the Houses of Parliament this morning, and our thanks go out to the quick and effective response of our police and medical services. Thank goodness the barriers are in place and worked.— Vince Cable (@vincecable) August 14, 2018 10:09AMCounter-terror expert: Chances of getting through barrier are very slim Chris Phillips, the former head of the National Counter Terrorism Security Office, said: “It looks a bit like a copycat of the incident from the other occasion, but however may be this is someone who has fallen asleep at the wheel, we don’t know as yet, so this is what the officers will be trying to ascertain.”I think the key point is the barriers around that building are designed to stop a vehicle travelling at 50mph, but the chances of getting through that barrier are very, very slim.”Of course, now the police officers need to make sure the vehicle itself is safe, that’s what they’ll spend most of their time doing.” Injured pedestrians can be seen at the top of the shot – around 40 metres from where the car crashed into a barrierCredit:BBC News/PA A bicycle lies on the ground after the Westminster attackCredit:Eddie Mulholland for The Telegraph Injured cyclists on the ground after the car crashed into themCredit:Twitter Bicycles lie on the ground at the scene of the crash outside the Houses of Parliament Credit:HANNAH MCKAY /Reuters A witness, who gave his name only as James, described how he had been cycling past Parliament shortly after the incident happened.”There was a cyclist clearly injured on the floor, there was a number of cyclists off their bikes. As I went past, an ambulance turned up,” he told the BBC Radio 4 Today programme.”As I carried on down I was told to get off my bike by a police officer. He said there’d been an incident. As I looked up as I got off my bike, I saw there was a car in the barrier.”My natural reaction was to get away from the scene.” Armed police swoop on a car that crashed outside the Houses of ParliamentCredit:VinnyMcAv/EuronewsNBC Ambulance crews treat the wounded after the Westminster crashCredit:UK Newsflare/AP 10:32AMTheresa May thanks emergency services for ‘immediate and courageous’ response Prime Minister Theresa May said her thoughts were with those injured in the Westminster car crash and thanked the emergency services for their “immediate and courageous” response.Meanwhile, Home Secretary Sajid Javid said: “Huge thanks to our emergency services for their rapid reaction to incident in Westminster this morning. My thoughts are with those injured.” After knocking down cyclists, the car mounts a pavement We’ve just heard that the Metropolitan Police’s counter-terror command is now leading the investigation.Scotland Yard said in a statement: “While we are keeping an open mind, the Met’s Counter-Terrorism Command is leading the investigation into the Westminster incident.” 9:59AM’There was a cyclist clearly injured on the floor’: Witness describes scene Six hours after the crash, the silver Ford Fiesta can still be seen near the Parliament barriers.A number of officers in forensic suits are working at the scene. 11:26AMPolice set to deliver update as Cobra meeting to be held at 2pm 9:49AMSecurity extended in wake of Westminster Bridge attack Aerial footage of the crash shows the silver Ford Fiesta coming along the road next to Parliament Square before moving to turn right towards Westminster Abbey.As an ambulance passes the car on its right-hand side, the vehicle swerves left – crossing oncoming traffic and a pavement before entering a small road and crashing into a security barrier.A police officer can be seen jumping another barrier that runs along the side of the road to get away. Westminster was in lockdown as armed police swarmed the scene. One witness said: “It looked intentional – the car drove at speed and towards the barriers.”Images showed a man being led away in handcuffs after armed police surrounded the eight-year-old car.A second image appears to show pedestrians hit by the vehicle at least 40 metres (130ft) away from where the car hit the barrier. 9:55AMSadiq Khan in close contact with Met Police chief 10:54AMExtra police officers put on patrol after Parliament crash Labour leader Jeremy Corbyn praised the emergency services in a tweet: 1:26PMTobias Ellwood: This is stark reminder of threats we continue to face Woody Johnson, US ambassador to the UK, wrote on Twitter that “America’s prayers are with all the innocent people hurt”, as he also praised the emergency services: 9:42AMCordon widened as more police arrive at scene More plain-clothed officers have arrived at the scene, as it appeared the number of armed police officers were stationed at a cordon beside Parliament were scaled back.Westminster Bridge and Tube station were both closed.The cordon was widened twice and sniffer dogs were seen scanning the area. I’m in close contact with @MetPoliceUK Commissioner about the incident at Parliament Square this morning. Thank you to the first responders who were on the scene so quickly. Enquiries are continuing. Westminster tube station is currently closed. Follow @metpoliceuk for updates. https://t.co/Uf2U85o0My— Sadiq Khan (@SadiqKhan) August 14, 2018 Another terrorist attack in London…These animals are crazy and must be dealt with through toughness and strength!— Donald J. Trump (@realDonaldTrump) August 14, 2018 My thoughts are with those hurt and injured outside Parliament this morning in what is being treated as a terrorist incident.Our thanks go to our emergency services who responded immediately. Their bravery keeps us safe day in, day out.— Jeremy Corbyn (@jeremycorbyn) August 14, 2018 Sadiq Khan, the Mayor of London, is in “close contact” with Metropolitan Police Commissioner Cressida Dick.He thanked the emergency services at the scene in a post on Twitter: Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.