A coward punch has left a man with serious head injuries. Herald Sun December 18,2016

A MAN is in hospital with serious head injuries after he was punched in the back of the head in a cowardly one-punch attack in Prahran yesterday morning.

Stonnington Crime Investigation Unit detectives are appealing for witnesses following the assault outside a bar early Saturday morning.

The attack happened as the victim walked past a group of men in Chapel St at 3.10am.

Investigators believe the group of four to five men had been evicted from a nearby bar shortly before the assault.

As the victim, a 33-year-old St Kilda man, and his friend walked past the group a verbal exchange took place.

The group surrounded the pair before some pushing and shoving began.

“As this was happening, one of the men walked around the group and punched the victim to the back of the head, causing him to fall to the ground,” police spokeswoman Creina O’Grady said.

The man then hailed a taxi and left the scene.

The victim was knocked unconscious and was taken to hospital with serious head injuries.

Police have released CCTV footage of a man they want to speak to.

Police are appealing for anyone who witnessed the incident to contact Crime Stoppers on 1800 333 000Herald Sun