Police arrested a man near London's Natural History Museum on Saturday after his vehicle mounted the pavement and ploughed into pedestrians, injuring himself and 10 others in an apparent road traffic collision unrelated to terrorism.
Witnesses and footage posted on social media suggested the man was pinned down on the ground by passers-by in the busy tourist spot.
"The incident is a road traffic investigation and not a terrorist-related incident," London's Metropolitan Police said in a statement.
"Whilst enquiries continue it is believed a car mounted the pavement and collided with a number of pedestrians."
It said the arrested man was among nine people taken to hospital, while two others were treated at the scene. He is currently in custody at a London police station.
No one is believed to have life-threatening or life-changing injuries.
The area, which includes the wide, semi-pedestrianised Exhibition Road which runs past the Science Museum and the Victoria & Albert Museum, is popular with families and tourists, particularly on a Saturday afternoon.
Footage and photographs posted on Twitter showed the detained man next to a black car with its door open and its bonnet severely damaged.
Witnesses reported by some media said they had heard a loud bang. An AFP reporter said crowds in the area had fled screaming in panic.
Armed police were deployed to the scene and the whole area was cordoned off.
Security is high in Britain after five terror attacks since March -- four of them in London and one in Manchester -- with the bloodshed claiming 35 lives.
Three of the attacks in London involved the use of a vehicle to plough into pedestrians.
Prime Minister Theresa May offered her thanks to the emergency services, adding: "My thoughts are with the injured."
'Everyone flew in panic'
London's Metropolitan Police said they were called to the scene at 2:21 pm (1321 GMT) after reports of a collision.
One witness, identified only as Katy, told LBC London radio she had seen two people injured, including a young boy whose leg was hurt and a woman.
Another who gave his name only as Leonard, told AFP: "I was near South Ken station and there were many police.
"Suddenly a police woman officer shouted at the crowd to run, and everybody flew in panic, many people screaming."
A spokesman for the Natural History Museum told AFP: "I can confirm that there has been a vehicle collision with pedestrians on our Exhibition Road entrance."
Not far away, tens of thousands of football fans took part in a silent protest "against extremism", walking from Park Lane past Downing Street and to parliament.
The Football Lads Alliance was formed after the London Bridge attack in June and brought together supporters of rival teams with military veterans.
Ahead of the march, founder John Meighan said the group wished to "show our concern at the recent upsurge in terror attacks taking place across the UK and Europe".