A man has been arrested after a car crashed into security barriers outside Britain's Houses of Parliament in Westminster, Scotland Yard says.
Dozens of emergency vehicles have been seen swarming around Parliament Square with members of the public ordered to stay clear of the area.
Video shows smoke coming from the bonnet of the vehicle and police officers urging people to leave the scene and find alternative routes.
Parliament Square has been closed as a result of the crash. Streets around Parliament Square, Millbank and Victoria Tower Gardens have been cordoned off as dozens of armed police swooped on the scene.
Armed officers could be seen surrounding the car before leading a man away in handcuffs.
"The male driver of the car was detained by officers at the scene. A number of pedestrians have been injured. Officers remain at the scene. We will issue further info when we have it," London's police force said in a statement on Twitter.
Footage on social media showed heavily armed police response units arriving at the scene.
Police said they could not immediately say whether it was a terrorism-related incident or not. "We're still trying to piece it together," a spokeswoman said. 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 on Britain last year which police blamed on terrorism. (Courtesy Sydney Morning Herald)