A man has been arrested by armed police and two people injured after a car crashed into security barriers outside the Houses of Parliament.

The Metropolitan Police said counter-terrorism officers are leading the investigation into the crash.

Armed police swooped on the vehicle following the crash at 7.37am on Tuesday, and the driver was taken away in handcuffs.

London Ambulance Service (LAS) said they treated two people at the scene for non-serous injuries and following this took them to hospital.

An eyewitness said that cyclists were among those injured, while another said that the car has been travelling "at speed - at least 50mph" when it appeared to "deliberately" crash into the barriers.

Jason Williams, 45, from Kennington, was walking to work when he saw the "car going at high speed towards Parliament...

"It looked deliberate. It didn't look like an accident. How do you do that by accident? It was a loud bang."

Streets around Parliament Square, Millbank, Victoria Tower Gardens and along Whitehall to the Cenotaph are all under a "Terrorism Act cordon", according to a police officer at the scene.

The cordon covers a large area, with the edges around a five-minute walk from the scene of the crash at Old Palace Yard.

More than 10 police cars, three ambulances, armed police and sniffer dogs remain on the scene.

Westminster tube station has been closed, although interchange between lines can still take place, and a number of buses are on diversion..

An eyewitness, 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."

ITV News Political Correspondent Paul Brand, who is nearby, said it appears that the "car has ended up in quite a specific spot, down what is effectively a slip road to leave the main road and enter the car park for the House of Lords".

A witness at the scene said that the crash "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."

Ewalina Ochab continued that the car did not appear to have a front registration plate.

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 said.

"The police said we had 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."

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.