Eleven people have been injured after a minicab driver struck pedestrians outside the Natural History Museum in west London, sparking a major security alert.

Scotland Yard said nine of those hurt were taken to hospital after the incident in Exhibition Road, South Kensington, at about 2.20pm on Saturday. No injuries were thought to be life-threatening or life-changing.

Those taken to hospital included the driver of the the black Toyota Prius, who is under arrest and in custody at a north London police station. Police said the incident was a road traffic investigation and not a terrorist-related incident. Officers are continuing their inquiries.

However, the heavy and swift response to the incident by dozens of armed officers reflected the concerns about a possible terror attack in the capital after the Westminster and London Bridge incidents this year.

The prime minister, Theresa May, tweeted: “My thanks to the first responders at this incident this afternoon and the actions of members of the public. My thoughts are with the injured.”

Pictures and video on social media showed street damage and a large police presence in the capital’s museum district, which is also home to the Science Museum and the Victoria and Albert Museum.

Video footage posted on Twitter showed a man being restrained on the ground in the middle of Exhibition Road. None of the four people surrounding him were in police uniform. A black Toyota car was behind them with the driver’s door open.

One witness, Lesley Carter, said passersby held the man down before police arrived. “I saw the man pinned down by about six people. It looked like the car had smashed into the wall between two other cars and the guy got out to run before being pinned down. Loads of people were running away and within minutes the police had turned up. It was a very quick response.”

The streets around the museum were cordoned off in the wake of the incident and South Kensington underground station was closed. By 4.30pm, police at the scene were telling curious tourists that the area was safe, but that an analysis was being carried out.

“I was serving some customers when the police came and just told everyone to run,” said a waitress from a restaurant on Exhibition Road, which was evacuated and cordoned off.

Another witness 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.”

A spokesperson for the nearby V&A Museum said it had not been closed to the public after the incident. The Science Museum also remained open but did not admit further visitors.