At least 40 people were injured when a terrorist attacker mowed them down on a busy central London bridge.
Five people have died, including one police officer, Met police have confirmed.
The attacker was driving a Hyundai i20 and struck a number of pedestrians crossing Westminster Bridge, before crashing the vehicle into fencing around Westminster Palace. He attempted to enter the Houses of Parliament, stabbing a police officer as he tried to force his way in.
The attacker was shot and killed by police.
One woman was pulled from the Thames river with serious injuries. It's not yet known whether she jumped into the river or was thrown in after being struck by the vehicle.
The Port of London Authority has confirmed that she was pulled from the river alive, requiring urgent medical attention.
Bus driver Michael Adamou told the Telegraph the woman jumped off the bridge to avoid being struck by the car, which had mounted the footpath and was hitting pedestrians.
"He must have come down the whole side of the bridge on the pavement. I would say there were at least 15 or 20 people [hit].
"When I was getting everybody off the bus, because they made us leave the bus on the bridge, I heard one guy come running behind me shouting his wife had jumped into the river to avoid getting knocked down."
Three French school pupils, five Korean tourists among injured
Two of the three injured French pupils are in a serious condition and are being treated at St Thomas' Hospital. The students were on a trip from Brittany, and it's believed they are between 15 and 16 years old.
A tour agency representative told South Korea's Yonhap News that four South Korean tourists "sustained light injuries and another [sustained a] serious injury."
Witnesses describe 'horrendous' scene
Footage captured by members of the public shows people lying injured on the bridge, with others running to their aid.
Two women witnessed the attack from on-board a double-decker bus.
"We heard what we thought were gunshots and then we saw this car just plow into this body," they told Channel 4 News.
"The body was trapped right underneath the front wheel. And then as the bus was pulling in slowly, just saw all these bodies that were spread out all the way along… from one end of the bridge to the other. It was horrendous. Absolutely horrendous."
Another witness described seeing the vehicle drive into pedestrians.
"I just saw a car go out of control and just go into pedestrians on the bridge," eyewitness Bernadette Kerrigan told Sky News.
"As we were going across the bridge, we saw people lying on the floor. They were obviously injured. I saw about 10 people maybe. And then the emergency services started to arrive. Everyone was just running everywhere," she said.
"Catastrophic" injuries have been described by doctors at St Thomas' Hospital, located right next to the bridge.
"There were people across the bridge. There were some with minor injuries, some catastrophic. Some had injuries they could walk away from or who have life-changing injuries," junior doctor Colleen Anderson said.
The Metropolitan Police are treating the attack as a "terrorist incident" and surrounding buildings are in lockdown. Scotland Yard believe there was just one attacker, and say Londoners should "be alert but not alarmed."
The incident has occurred on the first anniversary of the Brussels attack, during which 32 people were killed.