Teen charged after man punched unconscious

A 33-year-old man is in a serious condition after he was punched unconscious in front of police during an altercation in Western Australia's north.

Police were patrolling Roebourne just after midnight on Sunday when they stopped their car to speak with two men who appeared to be having an altercation, and the accused punched the victim to the head, causing him to fall to the ground.

The victim was taken to two hospitals before the Royal Flying Doctor Service flew him to Perth for treatment.

The 18-year-old accused man fled, but was arrested a short time later and charged with grievous bodily harm.