A man has been arrested and a number of people are injured after a car collided with security barriers outside Britain’s Houses of Parliament in London.

The area is in lockdown after armed police swarmed the scene on Tuesday morning.

Images posted to social media showed the suspect, wearing a black puffer jacket, surrounded by officers, being led away in handcuffs from a silver-coloured Ford.

“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 info when we have it,” London’s police force said in a statement on Twitter.

Two people were treated at the scene for injuries that are not thought to be serious, London Ambulance Service said.

Police said they could not immediately say whether it was a terrorism-related incident or not.

“We’re still trying to piece it together,” a spokeswoman said.

Parliament Square has been closed and the streets around Parliament Square, Millbank and Victoria Tower Gardens have been cordoned off.

Moment after the car crashed.

AAP

Westminster station is closed for entry and exit, Transport for London said.

Eyewitness Ewalina Ochab told the Press Association: “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 car did not appear to have a front registration plate when it crashed, she added.

Bus driver Victor Ogbomo, 49, was driving passengers past the front of Westminster when he saw the crash.

“All I saw was the smoke coming out of a vehicle, a silver vehicle … I just stopped the bus,” he told the PA.

“The police said we have to move back, then in less than five minutes the response team came.

“They went to the vehicle, so we had to push back. I saw the car in the barrier, I didn’t know how it got there.”

He said officers had their guns out when they arrested the driver.

Police activity in central London on Tuesday.

AAP

Members of the public and the media have been moved back from the area as police put up a “Terrorism Act cordon”, according to an officer at the scene.

The cordon extends past the Cenotaph on Whitehall – a five-minute walk from the scene at Old Palace Yard.

In March 2017, Khalid Masood, 52, killed four people on nearby Westminster Bridge before he stabbed to death an unarmed police officer in the grounds of parliament. He was shot dead at the scene.

It was the first of five attacks on Britain last year which police blamed on terrorism.