A man has been arrested after a car smashed into barriers outside London's Houses of Parliament.
London's Metropolitan Police said a number of pedestrians were injured in the incident but at this stage none of them are believed to be in a life-threatening condition.
The driver of the vehicle was detained by officers at the scene.
Video footage showed armed officers surrounding a vehicle that had collided with anti-terror bollards.
Police said they could not immediately say whether it was a terrorism-related incident or not.
The incident happened about 7:37 am local time, police said.
"We're still trying to piece it together," a spokeswoman said.
The nearby Westminster tube station has been cordoned off and Londoners are being urged to avoid the area.
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 in Britain last year which police blamed on terrorism.