The driver of a Mercedes is in hospital after an early-morning crash into a shopfront in the city.

Police, ambulance and DFES crews rushed to the scene near the intersection of Hay and William streets in Perth about 3.25am on Thursday.

The car reportedly reversed into a money exchange store, leaving the vehicle significantly damaged.

The driver of the white Mercedes-Benz CLA coupe, a man in his 50s, was unconscious when emergency crews arrived.

St John Ambulance took him to Royal Perth Hospital, where he remains in a stable condition.

Road policing group north officers are investigating the circumstances surrounding the crash.

A witness reported seeing police with evidence bags at the scene.