The man arrested over the Westminster car crash is in his 20s and is being held on suspicion of terrorist offences, Scotland Yard said.

The silver Ford Fiesta crashed into pedestrians and then security barriers outside the Houses of Parliament early on Tuesday morning.

Armed officers arrested a man at the scene and took him to a police station in south London. The Metropolitan Police said the suspect was not co-operating during questioning.

Two people were taken to hospital after being treated at the scene for injuries, which are not believed to be serious, the London Ambulance Service (LAS) said.

A third person was treated at the scene for minor injuries.

Scotland Yard said: "At 7.37am on Tuesday, August 14, 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."

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."

Prime Minister Theresa May said her thoughts were with those injured and thanked the emergency services for their "immediate and courageous" response.

Witness Ewalina Ochab told the Press Association: "I think it looked intentional - the car drove at speed and towards the barriers."

She continued: "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 car appears to have been driven through cyclists before ploughing into the security barrier.

Footage shot outside Parliament showed cyclists helping at least one biker laying on the ground as the LAS and armed officers arrived on the scene.

The Scottish Government said it was being kept informed of developments.

Justice secretary Humza Yousaf said on Twitter: "Thoughts very much with those injured in the Westminster attack.

"Police have said they are treating the incident as terror related. Important they are allowed to get on with the investigation and establish the facts."

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."

Mayor of London Sadiq Khan said "all Londoners, like me, utterly condemn all acts of terrorism on our city".

"The response of Londoners today shows that we will never be cowed, intimidated or divided by any terrorist attack," he said.

He added: "I have been and will continue to be in close touch with the Metropolitan Police Commissioner, Transport for London and the other emergency services.

"My heartfelt thanks goes to the brave first responders who were so quickly on the scene following the attack."

Mr Khan urged members of the public to "remain calm and vigilant", and report any information about the incident to the Metropolitan Police.

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.

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."