Update 6.10pm: Eleven people have been injured and a man detained by police after a car ploughed into pedestrians in one of London's busiest tourist areas, sparking a terror alert.
The incident sparked fears of a terrorist attack in an area busy with families, but Scotland Yard later confirmed it was being treated as a road traffic collision and was "not being treated as a terror-related incident".
The 11 people treated were mostly suffering from head or leg injuries, the London Ambulance Service said, with nine taken to hospital.
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."
Earlier: Several people have been injured after a car reportedly ploughed into people outside London's Natural History Museum.
Scotland Yard said that "a number of pedestrians have been injured" in an incident in Exhibition Road in South Kensington shortly after 2.20pm.
There’s been a serious incident outside the Museum. We are working w/ @metpoliceuk and will provide an update when we have more information— NaturalHistoryMuseum (@NHM_London) October 7, 2017
A Metropolitan Police spokesman said: "Officers are on scene, and the London Ambulance Service have been called.
"A man has been arrested at the scene.
"Inquiries to establish the circumstances and motive are under way."
Downing Street said that Prime Minister Theresa May is being kept up to date with developments.
Pictures and footage from the scene showed street damage and a massive police presence in the capital's museum district, home to the NHM, the Science Museum and the Victoria and Albert Museum.
The area is a magnet for tourists, including lots of children.
Afra Wang posted a picture of emergency services on Twitter, writing: "A crime scene? Full armed police locked the whole area out outside of @V_and_A in London. The helicopter above us doesn't seem to leave."
Video footage on Twitter showed a man being restrained on the ground in the middle of Exhibition Road.
None of the four people around him are in uniform.
Behind them is a black Toyota car with its driver's door open, which appears to have collided with a silver Vauxhall saloon.
An NHM spokeswoman said: "A vehicle has collided with pedestrians near the Natural History Museum entrance at Exhibition Road.
"The Museum's visitors and staff are always our first priority.
"We are working with emergency services to assess the incident and we are doing all we can."
An eyewitness at the scene 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."
London Mayor Sadiq Khan said: "Details are still emerging and I have spoken with and am in close contact with Assistant Met Commissioner Mark Rowley and our other emergency services."
Mr Rowley is the head of UK counter-terrorism policing.