A police officer and a woman are among 4 people who have been killed near UK Parliament in central London in what Scotland Yard are treating as a terrorist incident.
One of the people dead include the attacker and 20 people have been injured.
The woman was among several pedestrians struck by a car on Westminster bridge, before it crashed into railings.
An officer was stabbed in the Houses of Parliament by an attacker, who was shot by police.
Police said there were "a number of casualties" and a "full counter-terrorism inquiry" was under way.
Writing on Twitter, BBC home affairs correspondent Dominic Casciani said it is understood from multiple sources that two people were in the vehicle on the bridge.
Prime Minister Theresa May is to chair a meeting of the government's emergency Cobra committee later.
Source - BBC