Eleven people were injured when a car ploughed into pedestrians in one of London's busiest tourist areas.

A man was arrested near the Natural History Museum (NHM) in South Kensington on Saturday afternoon.

The incident is not being treated as terror-related, the Metropolitan Police have said.

Video footage posted on Twitter showed a man being restrained on the ground in the middle of Exhibition Road in front of what is believed to be a Toyota Prius minicab that had collided with a silver Vauxhall saloon.

Tommy Gallagher, 37, had just been to the NHM with his six-year-old son when the incident happened.

He told ITV News: "It just went mad. People were screaming 'run, run'. It was a stampede.

"Some poor woman and a child in a pram were trampled over. It was horrible.

"My little boy thought a monster was chasing us."

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 families with young children.

Downing Street said that Prime Minister Theresa May is being kept up to date with developments.

Scotland Yard said that "a number of pedestrians" were hurt in an incident in Exhibition Road in South Kensington shortly after 2.20pm.

A Metropolitan Police spokesman said: "Officers are on scene, and the London Ambulance Service have been called.

"A man has been detained at the scene.

"Inquiries to establish the circumstances and motive are under way."

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 pinned to the ground. None of the four people around him were in uniform.

Behind them is the black Toyota with its driver's door open.

American couple Annie Cutting and Joseph Degraff, both 23, were caught in the aftermath as they sat in a cafe on Exhibition Road while on holiday in the capital from Washington DC.

Mr Degraff said: "We saw a large stampede of people running and thought, 'what's going on?'

"Someone who works in the cafe said, 'get on the ground'.

"We hit the floor. We were there for a few seconds, then they told everyone to get in the basement.

"At that point I thought it was a shooting or a bomb or something. We just didn't know.

"The police told everyone to get out of the cafe and we got out and ran."