Police are on the scene of a “serious injury accident” involving a taxi and pedestrians in central London.
Scotland Yard said the incident on Southampton Street, Covent Garden, is not thought to be terrorist related.
Officers were called at just after 5pm to reports of a taxi in collision with pedestrians.
London Ambulance Service said it had crews at the scene.
The driver stopped at the scene and had been detained, police said.
“We are aware of injuries but await further confirmation,” a Scotland Yard spokesman added.
“This is being treated as a serious road traffic collision, and not thought to be terrorist related.”
Photographs on social media showed a black taxi on the pavement behind orange roadworks barriers outside the Jubilee Market Hall.
A number of bystanders appeared to be helping injured people on the ground beside the vehicle.
Witness Ed Hoppitt posted: “Just came within meters of being hit by a vehicle that mounted the pavement and ploughed into people. #CoventGarden people down under taxi.”
Four people were injured in the incident, with three taken to hospital and a fourth treated at the scene, paramedics said.
Stuart Crichton of London Ambulance Service said: “A man was treated for a serious leg injury and taken to a major trauma centre as a priority.
“Two other patients were treated for minor injuries and also taken to hospital. A fourth patient was checked over at the scene.”