'A woman flipped over the side of the bridge': Witnesses recount horror London terror attack
A man has gone on a rampage, running down pedestrians on London's Westminster Bridge before stabbing a police officer to death outside parliament.
Police have revised the death toll to four with 29 people injured and seven critical after the terror unfolded at the popular London strip.
British Prime Minister Theresa May has confirmed the attacker was a British-born man who had previously come to the attention of authorities due to concerns about his "violent extremism".
"Some years ago, he was once investigated by MI5 in relation to concerns about violent extremism," Ms May told parliament.
"The case is historic, he was not part of the current intelligence picture.
"There was no prior intelligence of his intent or the plot."
The attacker, who was shot dead after stabbing a police officer to death, is yet to be named.
Horrifying footage emerged of the moment a woman plummeted into the River Thames as the man's car mounted the pavement on the bridge during the attack.
The woman can be seen soaring into the icy cold waters as the grey SUV comes speeding along the pavement.
It is unclear if she jumped or she has tumbled over as a result of the van coming past.
Witnesses saw the woman land in the water, she was rescued and is reportedly recovering in hospital.
Steve Voake described the mayhem on the bridge.
"There was a woman at the top of the steps, her head was just pulsing with blood and bleeding out and there was another woman who flipped over the side of the bridge," he told the London Telegraph.
After the car drove into the crowds on the bridge it continued on and crashed into the gates of parliament.
The driver was later shot dead by other officers.
Several witnesses have described accounts from the bridge and of the attack on policeman Keith Palmer.
London photographer Toby Melville described the horrifying moment he discovered a man had fallen from the bridge.
"I heard a thud, turned round and there was a man lying about 10 yards away from me," Mr Melville said.
"There was a lot of blood coming from his head. I thought this must be a domestic or horrible accident.”
He immediately phoned emergency services before climbing the steps up to the bridge to discover a scene of utter chaos.
"Of a dozen or so people, some of them seemed to be conscious. I didn't know there had been a vehicle involved at the time, someone said 'bus', someone said 'car' someone said 'shooting'," he said.
He immediately phoned emergency services before climbing the steps up to the bridge to discover scenes of utter chaos.
"Of a dozen or so people, some of them seemed to be conscious. I didn't know there had been a vehicle involved at the time, someone said 'bus', someone said 'car' someone said 'shooting'," he said.
Witness Steve Voake told the Telegraph the first thing he noticed was a trainer on the road.
“I looked more closely I saw that there were a couple of bodies the other side of the road," he said.
“And when I looked over the side there was another body lying in the water with blood all around it.
"There was a woman at the top of the steps, her head was just pulsing with blood and bleeding out and there was another woman who flipped over the side of the bridge. Someone landed in the river somewhere," another witness told reporters.
Rick Longley saw the armed assailant stab officer Keith Palmer to death.
"We were just walking up to the station and there was a loud bang and a guy, someone, crashed a car and took some pedestrians out," Mr Longley said.
"They were just laying there and then the whole crowd just surged around the corner by the gates just opposite Big Ben.
"A guy came past my right shoulder with a big knife.
"I have never seen anything like that. I just can't believe what I just saw."
As he turned onto Westminster Bridge to the sounds of gunshots, bus driver Michael Adamou was confronted with the sight of countless bodies lying motionless on the footpath.
"As I turned left out of Whitehall, so turning left to go over the bridge, I saw a car knock two people over," he said.
"Initially I thought he's lost control of the car, but then I saw quite a few people rushing into Parliament and police trying to stop everyone.
"After a few seconds I just heard gunshots. Everybody on my bus was panicking."
Another man said he could see “at least eight figures on the west pavement” seconds before the rampaging car crashed at the south end of the bridge.
US tourist Bradford Buck said "police cars just kept coming one after another after another, I've never seen such a quick response”.
The identity of the attacker, who was shot dead, has not been released by police.
Officers said he has been identified, but said his name would not be released while officers continue to investigate.