A man is in Auckland Hospital after he was found injured on the side of a Waiheke Island road by a passing motorist.

St John Ambulance said a man was flown to Auckland Hospital by rescue helicopter following an assault.

The man needed treatment for a puncture wound to his upper body.

A police spokesman said the man had been knocked on the head and suffered a puncture wound but it was unclear what caused the injuries.

Advertisement

A passing motorist driving along a Waiheke road spotted the injured man and raised the alarm around 11pm.

Police said they hoped to speak with him in coming days to determine what happened.