Injured man found on road in north Sydney

A man found lying injured on a road in Sydney's north was the victim of an assault, police say.

The 56-year-old was taken to Royal North Shore Hospital for a non-life threatening injury to his head after he was found on West Street at Crows Nest late on Thursday night.

Police have set up a crime scene and searched the area with the help of the dog unit but found no persons of interest.