London attack: Pictures from Westminster terror attack
- Published
Four people, including a police officer and an attacker, died and 40 others were injured in the attack at the Palace of Westminster and Westminster Bridge.
Emergency services sealed off the area just after 14:40 GMT after an officer was killed and his attacker shot by armed police inside the gates.
An air ambulance landed in the middle of Parliament Square as medics rushed to help.
MP Tobias Ellwood tried to help save the officer after he was stabbed by giving mouth-to-mouth resuscitation.
Nearby, police could be seen holding a gun to a man on the cobbles inside the grounds of the palace.
The suspect was taken to a waiting ambulance on a stretcher. He was later confirmed to have died.
The prime minister was taken by police back to Downing Street from the House of Commons.
Armed police looked after visitors inside Parliament as the Commons was suspended and the site went into lockdown.
Ambulance crews were treating people on Westminster Bridge and on the road down to Parliament Square after a car hit pedestrians.
They treated several people who were hit by the car, before it was driven into the railings of Parliament.
Those injured on the bridge were helped from the scene. Some had "catastrophic" injuries.
Tourists and Londoners were caught up as roads were closed.
They rushed from the bridge and headed away from Parliament Square.
Tourists travelling on the London Eye at the time of the incident were stranded for three hours.
"This was a day we've planned for but hoped would never happen," said the Met Police's Head of Counter Terrorism Mark Rowley.
Patrol boats were out on the Thames. A woman was pulled from the river and treated for injuries.
People were told to avoid Parliament Square, Whitehall, Lambeth Bridge, Victoria Street to the junction of Broadway, and the Embankment between Westminster and Embankment Tube.
The attacks unfolded as the Scottish Parliament was debating holding a second referendum, where proceedings were stopped.
Prime Minister Theresa May ordered flags to be lowered to half mast on government buildings as a mark of respect to those who died.
Police and intelligence services remained on the scene into the evening as they continued their investigation into the Westminster attack.
In a statement outside Number 10, Mrs May called the attacks "sick and depraved". She said the streets of Westminster were "ingrained with a spirit of freedom" and "any attempt to defeat those values through violence and terror is doomed to failure."
The police officer killed in the attack at Westminster was later named by Scotland Yard as PC Keith Palmer. The 48-year-old husband and father was a member of the Met's parliamentary and diplomatic protection command and had 15 years service.
Flowers were laid at the scene close to the scene of the attack. Forty others have been injured.