Eleven people were injured after a car ploughed into a crowd in London’s busy museum district sparking a terror alert.
Police arrested a man after a black Toyota car mounted the pavement and careered into pedestrians outside the Natural History Museum in South Kensington on Saturday afternoon.
It sparked fears of a terrorist attack in an area packed with tourists and families but Scotland Yard said it was being treated as a road traffic collision and was not a terror-related incident.
Nine of the injured were taken to hospital and most of the people hurt suffered from leg and head injuries, London Ambulance Service said.
Their injuries were not life-threatening or life changing.
Met Police were called to reports of a collision at 2.20pm in Exhibition Road and a man was arrested at the scene.
Images showed a man in a blue shirt being pinned to the ground. Other pictures showed a damaged black Toyota Prius, registered as a minicab, that had collided with a silver Vaxuhall saloon and a Jaguar.
Singer Pixie Lott's model fiance Oliver Cheshire, 29, said he was one of three men who helped to detain the driver. In a message posted on social media: "Thanks for messaging everybody. I'm OK.
"Thank you to the men who helped me pin him down and the police for coming so quickly."
Witnesses described hearing a loud bang and seeing scores of people running into the museum in a panic.
Sophie Parry and Lesley Guinness were on their way to the V&A's Pink Floyd exhibition when they saw the driver of a black vehicle swerve across the road and hit a cyclist.
First aid-trained engineer Ms Parry, 56, said: "We saw a black mini SUV - it suddenly swerved across the road and it appeared to knock a cyclist off their bike, and the cyclist was sort of being carried along on the front of the vehicle across the road and then the black car hit another car - a silver Vauxhall - and it appeared to throw the cyclist off.
"By the time we came across the road two people were helping this person in the road and it looked like they were administering first aid or just comforting them."
Ms Parry said she believed the cyclist was a man in his twenties, and did not appear to be wearing a crash helmet.
Both women said the front of the car was "pretty smashed up" and may have hit some nearby concrete bollards.
Ms Parry said: "I thought maybe someone might have had a heart attack behind the wheel.
"Because I thought, this is strange for a vehicle - it must have been going pretty slow there to career across and do all that damage.
"It's odd, because any vehicle there was maybe going three, four, five, six miles an hour. So I thought maybe someone had had a heart attack or something."
The friends said they saw people running away from the scene, after three "gunshot-like" bangs rang out a few seconds before the cyclist was struck.
Dieon Rurora, 25, who works in a nearby cafe, added: "People were running down the street, falling over. It was quite scary."
One tourist told the Standard that the car mounted the pavement and sent terrified crowds fleeing in all directions.
Pictures and footage showed street damage and a huge police presence in the capital's museum district, home to the Natural History Museum, the Science Museum and the Victoria and Albert Museum.
The area is a magnet for tourists including lots of children.
London Mayor Sadiq Khan said: "I would like to thank our police and other emergency service first responders for their swift reactions and also passers-by for remaining calm.
"All those injured are in our thoughts and we hope they all make a swift recovery."
Downing Street had said that Prime Minister Theresa May was being kept up to date with developments.
One tourist, who asked not to be named, told the Standard he was queuing for the museum when the car mounted the pavement and sent terrified crowds running in all directions.
He said: “We were in the queue for the Natural History Museum when it happened.
“We just saw people running, scared, and then people in the queue started running too.
“Everyone was terrified, nobody knew what had happened.”
Another eyewitness said: "We were walking near the Science Museum and heard a bang, bang... at first I thought it was gunfire.
"Then we walked past the scene of the accident and saw a guy pinned down by other men and lots of people calling the police.
"There didn't appear to be many people hurt - a few sat by the side of the road but more looking shaken than anything.
"We were then ushered into the Science Museum and the area was quickly cleared of pedestrians."
Damian Hackett, who witnesses the aftermath, told the BBC: “When we arrived there the incident had already taken place and the police were responding so they were milling about trying to get people away from the area.
“They set up a cordon immediately we were standing there for a moment trying to figure out what do we do, what’s happening here. We didn’t know what was going on.
“And then police came more or less charging towards the crowd and everybody was just starting to get out of there now. We all legged it basically, there were tables knocked over at restaurants, people were screaming. It was quite a scene at that stage.
“I heard one policeman shouting “run and don’t stop running.”
Jane Witherspoon was getting off the Tube at South Kensington station to go the Natural History Museum when people began rushing in.
She told Sky News: “I was getting off the Tube a South Kensington and about 50 people came rushing down the escalator. Some of them were cowering in the walkway.
“It was mass panic really.”
She added: “There was an announcement asking everybody to immediately leave the station. We jumped back on and we thought that the safest thing was just to go to the next station.”
The Natural History Museum and Tube stations including South Kensington and Sloane Square on the Circle and District Line routes were evacuated. The V&A remained open.
A Metropolitan Police spokesman said: "Whilst inquiries continue it is believed a car mounted the pavement and collided with a number of pedestrians.
"Eleven people were found at the scene with varying injuries and nine of them have been taken to hospital, and this includes the man that was detained by police.
"Their injuries are not believed to be life-threatening or life-changing.
"The man detained by officers is currently under arrest and is in custody at a north London police station.
"The incident is a road traffic investigation and not a terrorist-related incident."
A London Ambulance Service spokesman said: "We sent multiple resources to the scene, including our hazardous area response team, ambulance crews, paramedics in fast response cars and incident response officers.
"We have worked closely with other members of the emergency services at the scene with our priority being to get people to safety and ensure they received the medical help they needed as quickly as possible."
Anyone with information is asked to call police on 101.