Facebook has activated its Safety Check feature in the wake of the Westminster terror attack.

Users can mark themselves as safe here, and see a list of their friends in the area.

The social network switches the feature on after major incidents, allowing people to quickly let their friends know that they've not been harmed.

Users can also share the London Safety Check on their own timeline or that of a friend, as well as in a group, page, event and private message.

A police officer was stabbed outside the Houses of Parliament earlier this afternoon, with the alleged assailant, who reportedly also ran over members of the public on Westminster Bridge, shot by armed police shortly afterwards.

Four people have been confirmed dead, including the attacker and the police officer who was stabbed.

At least 20 people have been injured.

Meanwhile, a bomb squad has been called to investigate a suspicious vehicle parked near Parliament.

Metropolitan Police have warned people to stay away from certain areas in central London.

Anyone with information is being urged to send pictures and video footage to the National Police Chiefs' Council.