Workers in a cafe near the Natural History Museum say they fled the scene in fear.
According to her, the scene immediately arrived armed police, in the sky circling police helicopter.
Mark added: 'I think everyone seems to be just trying to carry on as normal because no one knows what is happening'.
The Metropolitan Police had confirmed the incident, which injured 11 people, as a "road traffic collision" and not terrorist related soon after it created panic in the busy tourist spot in the British capital.
Police said 11 people were injured when a vehicle apparently mounted the pavement and hit pedestrians.
He said none of the head and leg injuries turned out to be serious and that most of the nine people who had been hospitalized have been discharged.
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The HTS-linked Ibaa news agency did not mention the attack but said Russian warplanes were bombing areas the group controls in northern Syria.
A man arrested after a minicab crash sparked a terror alert in London's museum district has been released by police. The incident is not terrorist-related, police said. Earlier, authorities had said a man was arrested, CNN reported.
A large police presence descended on Exhibition Road, South Kensington, yesterday afternoon after a black Toyota Prius hit people outside the museum at about 2.20pm. "A crowd gathered around, and one or two people lying on the ground", she said. Did you go to the fantastic Natural History Museum, or watch the changing of the guards at the palace?
Witness Katie Craine said she was coming out of the museum when she saw a man in handcuffs pinned down by police near a damaged auto.
The South Kensington tube station has been temporarily shut down in the aftermath.
The UK is now under a "severe" level of threat of terror attack, according to the MI5 Security Service's rating system. Now the police are investigating this event.
There have been five attacks described officially as terrorism this year, three involving vehicles.
In the month of March, Khalid Masood killed four people and left more than 50 injured in a similar fashion at Westminster Bridge.