Police are at a "terrorist incident" at the Palace of Westminster and Westminster Bridge where four people, including a police officer and an attacker, have died and 20 others have been injured.
Emergency services sealed off the area just after 14:40 GMT after an officer was killed and their attacker shot by armed police inside the gates.
Ambulance crews were treating people on Westminster Bridge and on the road down to Parliament Square after a car hit pedestrians, killing two people.
Police could be seen holding a gun to a man on the cobbles inside the grounds of the palace.
He was taken to a waiting ambulance on a stretcher.
The prime minister was taken by police back to Downing Street from the House of Commons.
Armed police looked after visitors inside as Parliament was suspended and the site went into lockdown.
People injured on the nearby bridge were helped from the scene by the emergency services. Some had 'catastrophic' injuries.
Crews worked on several people who were hit by a car before it was driven into the railings of Parliament.
Tourists and Londoners were caught up as roads were closed.
They rushed from the bridge and headed away from Parliament Square.
Patrol boats were out on the Thames. A woman was pulled from the river and treated for injuries after she apparently jumped in.
People have been told to avoid Parliament Square, Whitehall, Lambeth Bridge, Victoria Street to the junction of Broadway, and the Embankment between Westminster and Embankment Tube.
Source: BBC News:
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