A Dunedin teenager remains in a serious condition in hospital, following a brutal attack outside a party.

The 17-year-old boy underwent surgery yesterday, for a badly fractured jaw.

He was beaten by four or five other teenage males outside a Malvern Street house, while a party was taking place nearby on Saturday night.

Police are investigating the attack, believed to have been unprovoked.

The teenager was repeatedly kicked in the head and body sometime between 10.30pm and midnight.

Police are speaking to witnesses and are confident they'll identify those responsible.