Two people have been injured and a man has been arrested after a car crashed into security barriers outside parliament.
A silver car crashed into security barriers in Westminster at 7.37am, prompting a huge response from armed police.
It is being investigated by counter-terror officers.
The driver, wearing a white shirt and a black hooded puffer jacket, was detained at the scene.
The black man was led backwards away from the silver Ford after police held him at the scene for a few moments.
London Ambulance confirmed they treated two people at the scene, and took them to hospital.
Their injuries are not believed to be serious. In a statement, Scotland Yard said: “At 7.37am today, a car was in collision with barriers outside the Houses of Parliament.
“The male driver of the car was detained by officers at the scene. A number of pedestrians have been injured. Officers remain at the scene.
“We will issue further information when we have it.”
At 8.40am they added: “At this stage, officers do not believe that anybody is in a life-threatening condition.
Cordons are in place to assist the investigation. Westminster tube station is closed.”
A later update added: “While we are keeping an open mind, the Met’s Counter-Terrorism Command is leading the investigation into the #Westminster incident.”
Reports suggest people are being held inside Westminster station at police request.
According to Vincent McAviney, the police radio reported the incident would be treated as “counter-terror”.
Ewalina Ochab told the Press Association: “I think it looked intentional – the car drove at speed and towards the barriers.”
She said: “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 car she added.
According to witness reports, cyclists have been seen “lying in the road” after the crash.
Streets around Parliament Square, Millbank and Victoria Tower Gardens have been cordoned off, with the cordon moving further away from the scene.
Sky’s political reporter Aubrey Allegretti said he has been told the area around Millbank’s offices has been “sanitised”.
There are “dozens” of armed police and 10 cars on the scene and police sniffer dogs have been used.
Armed police were seen leading the driver away in handcuffs, and a number of ambulances are at the scene.
Several armed police appeared to be leaving the scene by 9.30am, seemingly being “stood down” from the incident.
Parliament is in summer recess, and so there are fewer politicians working in London, but there are numerous other people working nearby, including political journalists. MI5’s headquarters is also nearby.
One man who witnessed the crash told Sky News it was “very very dramatic”.
He added: “I seen smoke coming out of a vehicle. It’s all been high speed – you’ve got the specialists coming in… it’s been dramatic.”
Bus driver Victor told Sky News: “I stopped the bus because of the crash, and police told us to ‘move back’. “I think it’s not a regular traffic accident, because there’s a barrier there. So I don’t know why someone would drive into the barrier. “I saw someone was arrested, but I couldn’t see him closely. He was taken away very quickly.”
Sky’s policing analyst Graham Whetton said police would be looking at the scene once it was sealed off, and would be assessing the route in the car would have taken.
He said: “They would go immediately to a counter-terror cordon and that enables the officers to work comfortably and quickly.
“The officers will be looking at the actual scene itself, the route the vehicle came in and trying to establish who is behind it and the reason why – and if there is any support network helping this individual – or if it’s just literally someone who has had a road traffic collision.
“That vehicle is likely to remain in place – they want to make sure it’s got nothing in it that’s suspicious before they go in and examine it.
“In any incident like this… we’ve got so many other important venues and locations, they will be increasing visibility and security patrols just to make sure nothing else happens.
“Those vehicle entrance points are the most vulnerable of parliament… The armed officers there are probably the most highly trained and they will only use their firearms if there is a threat to life.”
Chris Phillips former head of the National Counter Terrorism Office: “It looks a bit like a copycat incident – but maybe, it’s someone who has just fallen asleep at the wheel. We don’t know as yet and that’s what officers will be trying to ascertain.
“The officers need to make sure that vehicle is safe.
“The key point is the location – if this had happened anywhere else in London we wouldn’t have had this response.
“The area the car has gone down… that is an attempt to get into the Palace of Westminster.”
Dr David Lowe, terrorism expert at Leeds Beckett University, said: “If it is a deliberate act, then let’s see what is the motive behind it.”
Former Met Police chief inspector Peter Kirkham told Sky News: “It’s inevitable it’s going to be investigated as an attack in view of the location of the incident.
And certainly the initial assessment of the incident doesn’t seem like a normal traffic accident.
“The eyewitness statements all seem to point towards it being a deliberate attack, and where the car ended up… “That said it doesn’t look like [the police] have many concerns about the vehicle being a threat.
There are many people milling about close to it. If police thought it was a viable device, then the cordon would have been a lot wider than it is.
“It could be a deliberate attack but for other reasons – a protest attack for example. But initially, police will want to cross off the possibility of a terrorist attack.”
Tom Parmenter, Sky’s political correspondent, said: “The police response is very significant indeed. In the initial stages we saw sniffer dogs.
“All the time we are getting officers arriving at the scene. Some of them plain clothes, some of them in uniform. The cordon is stretching significantly.
“The judgement of the emergency services is that their response is proportionate to the incident they are dealing with.
“We still don’t know the motive for why that car drove at those barriers.”
Steel and concrete barriers were added outside parliament after the 2017 Westminster Bridge terror attack.