Six people were injured on Sunday and rushed to hospital after a car taking part in an Oslo motor show drove into the stands, police said.

Police initially wrote on Twitter that six people were taken to hospital "for further checks", but later said the number may have been higher as some others made their way to hospital independently.

The cause of the accident was not immediately known. It occurred at a motor show held in a car park outside a harness horse racing track.

Video footage showed a car reversing at high speed, with the driver appearing to lose control as the car swerved into the crowd standing beside the car park.

The severity of the injuries was not immediately known.

"The injuries are serious for at least one of them. I have no other details about the injuries," police chief Thomas Broberg told reporters.

He said police had spoken to the driver of the car and had "a theory" about the cause of the accident but said the investigation would take time.

Some of the injured were children, Broberg added.