Injured man found on Sydney road

A man is in a critical condition after being found lying on a road in Sydney's east but police don't know if he was the victim of a hit-and-run or skateboarding accident.

A passing motorist found the 26-year-old man lying on St Thomas Street in Bronte about 2am on Wednesday.

Paramedics treated him at the scene and he was rushed to St Vincent's Hospital in a critical condition.

Police say a skateboard was found nearby.