Police are appealing for witnesses after two men were assaulted in St Kilda on Saturday night.
Investigators were told three male offenders attempted to gain entry to a licensed premises on Ackland Street about 9pm on 21 December.
It is believed one of the males was refused entry and punched a security guard before the two other males punched and grappled with the victim.
Police were told a man wearing a baseball cap attempted to intervene and was punched by the offenders while they continued to assault the security guard.
Both victims were taken to hospital with non-life threatening head injuries.
The suspects ran from the scene east along Ackland Street towards Barkly Street.
Police have released images of three men who may be able to assist with their enquiries.
The first man is believed to be Caucasian in appearance with a slim build, short dark hair and a heavily tattooed right forearm and right calf.
The second man is believed to be Caucasian in appearance, of slim build with short dark hair.
The third man is believed to be Caucasian in appearance and of medium build with a beard and was wearing a Santa hat.
Anyone who witnessed the incident or has information as to the identity of the men in the images is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report on www.crimestoppersvic.com.au