A man has been killed after he was pinned under a bus that crashed into a restaurant at Haymarket in central Sydney.

The Imperial Pacific coach crashed into the awning of a Chinese restaurant, the Emperor’s Garden, about 12:00pm, after striking the man, who died at the scene.

The man’s body remains trapped under the bus. It is unclear why the bus crashed.

Witnessed described hearing a large bang followed by the sound of twisting metal. Some told the ABC the driver nearly ran over over pedestrians when he reversed after hitting the awning.

The area has been cordoned off and police and paramedics are on the scene, with hundreds of shoppers and pedestrians looking on.

Inspector Malcolm Searle from New South Wales Police says the cause of the crash remains under investigation.

“It appears as though… the driver may have suffered from some sort of a medical episode,” he said.

Given the busy location of the crash, Inspector Searle says it is fortunate there are not more casualties.

“I dare say [the bus] did come close to other pedestrians… perhaps not for the awning, the bus may have caused further damage,” he said.

Police say the bus, which was carrying the driver and one other person, was on its way to a job.

Inspector Searle is urging witnesses to contact police.

Andrew Pitt, who was sitting just metres away from the accident site, says he did not immediately realise that someone had been hit.

“I heard the bus hit the awning, it stopped, there was a lot of screeching of metal,” he said.

“People cried ‘stop, stop, stop’.”

Other witnesses told the ABC that, after the crash, the driver nearly ran over pedestrians when he reversed in an attempt dislodge the vehicle from under the awning.

The area has been cordoned off and police and paramedics are on the scene, with hundreds of shoppers and pedestrians looking on.

The driver of the bus, who is aged in his late 50s, was treated by paramedics and taken to the Royal Prince Alfred hospital for further tests.

“He doesn’t appear to have any injuries that are considered serious,” Inspector Searle said.

“He’s essentially being treated for shock.”

Police say it could be several hours before the victim’s body is removed.