A man remains in a serious condition in hospital after being punched in the back of the head outside a Christchurch bar.

A witness said on early Sunday morning, a group of young men walked up to a man who was walking into Rock Pool on Hereford Street, when one of them punched him in the back of the head, knocking him to the ground.

“There were about 12 offenders. They first attacked a group of younger boys first, but the first guy they hit in the back of the head suffered the worst injuries.

They ran off as soon as the police were called.”

A police spokesman confirmed police attended reports of two people fighting outside a bar on Hereford Street Christchurch at 12.20am on Sunday.

A man was assaulted and was taken to hospital, and a man was arrested in relation to the assault and inquiries are continuing. Police are yet to lay charges.

The victim remains in the hospital in a serious, but stable condition.

Chris Lynch Media understands the victim was placed in an induced coma.