LONDON - A number of people were injured when a car collided with security barriers outside London's parliament building on Tuesday and the driver was arrested, police said.
Police said none of the injuries were life-threatening and they could not immediately determine whether the incident was terrorism-related.
"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.
A spokeswoman said: "We're still trying to piece it together."
Footage on social media showed a handcuffed man being led away by heavily armed police.
"Someone driving toward parliament at speed, it wasn't a normal, it's not a minor like accident, it's not like a road traffic incident," witness Jason Williams told Sky News. "This is something in my opinion planned and very serious."
Television images showed police pointing their guns at a vehicle which appeared to have entered a lane used for access to the parliament building before it stopped at a security barrier.
Media reports said a cyclist was among the injured.
Westminster Underground station, close to parliament, was closed and the building cordoned off. No one was being allowed entry to parliament. As parliament is in recess for summer, most lawmakers are not using the building.
The crash occurred at 0637 GMT.
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.
Britain is on its second highest threat level of "severe", meaning an attack by militants is considered highly likely.
Last week, a Muslim convert admitted plotting to kill more than 100 people by driving a truck into pedestrians on London's Oxford Street, the capital's major shopping thoroughfare.