The Metropolitan Police will step up its armed presence in London's streets after a car crashed into several cyclists and pedestrians before smashing into barriers outside Westminster .

A man in his 20s has been arrested on suspicion of terrorist offences, the force confirmed shortly after the incident.

Multiple people were injured when the silver Ford Fiesta smashed its way towards the gates outside of the House of Common at 7.37am on Tuesday (August 14).

Police confirmed the incident is being treated as an attempted terrorist attack and its Counter Terrorism Command Unit is now leading the investigation.

Londoners have been warned to not be alarmed by additional police presence as British Transport Police (BTP) officers - both armed and unarmed will be carrying out patrols across the capital.

A car crashed into security barriers outside the Houses of Parliament

The area around the Palace of Westminster was temporarily in lockdown as police swarmed the scene after a car crashed into several people before smashing into the barriers.

Video footage from the scene shows officers swooping the area where they arrested the suspected driver who has since been taken to a south London police station where he remains in police custody.

Officers remain at the scene to carry out searches however a weapon has not yet been recovered, the force confirmed.

Streets around Parliament Square, Millbank and Victoria Tower Gardens and Westminster tube station will remained closed until further notice.

Police activity on Millbank, in central London

"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," said Superintendent Chris Horton from British Transport Police

"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."

In a statement a force spokesman said: "At this stage, we are treating this as a terrorist incident and the Met's Counter Terrorism Command is now leading the investigation.

"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.

"A number of people were injured as a result of the collision and they have been taken to hospital.

"At this early stage none of the injuries appear to be life-threatening."