Police Treating London Parliament Car Crash As 'Terrorist Incident'

The driver, a UK national, has been detained on suspicion of terrorist offences.

British counter-terror police are investigating after a car hit pedestrians and crashed into security barriers outside British parliament in London.

The driver of the car, a 29-year-old man who is a UK national, was detained on suspicion of terrorist offences following the incident about 7.30am on Tuesday (4.30pm AEST) during which three people were injured.

A man and a woman who were taken to hospital with non life-threatening injuries have since been discharged, Metropolitan Police said in a statement.  A third person with minor injuries was also assessed at the scene.

Forensic officers work by the car that crashed into security barriers outside the Houses of Parliament. Image: AAP

Detectives said the car, a privately-owned Ford Fiesta, travelled from Birmingham to London late on Monday night (local time).

The 29-year-old driver was arrested at the scene and remains in police custody.

Metropolitan Police Assistant Commissioner and National Lead for Counter Terrorism Policing Neil Basu said investigators believed a man deliberately drove a car into pedestrians before crashing into barriers, and that the arrested suspect was not co-operating.

“Given that this appears to be a deliberate act, the method, and this being an iconic site, we are treating it as a terrorist incident," the statement from Metropolitan Police said.

Metropolitan Police Assistant Commissioner and the National Lead for Counter Terrorism Policing in the UK Neil Basu addresses the media. Image: AAP

Counter-terrorism police are searching three properties in the Midlands, in central England as part of their investigation.

"At this stage, there have been no other arrests in connection with this investigation," the statement said.

"There is no intelligence at this time of further danger to Londoners or to the rest of the UK connected to this incident."

Video from the scene showed a heavy police presence, with multiple officers bearing heavy arms, and a heavily-damaged silver car crashed into a barrier.

Police and ambulances were on the scene, with large parts of the area cordoned off with tape.

US President Donald Trump tweeted his reaction to the crash, writing "These animals are crazy and must be dealt with through toughness and strength!"

Authorities said there was no one else in the car and no weapons have been recovered at this stage.