Prime Taskforce detectives are appealing for witnesses after concerning behaviour during a protest last month where a man was assaulted, spat on and had urine thrown on him.
The victim was walking amongst protesters on Swanston Street near Franklin Street, when he was attacked by three men about 11.15am on Tuesday, 21 September.
The first man, who grabbed the victim by the neck, is perceived to be Caucasian in appearance with dark hair and wearing a green and grey hi-vis hoodie, dark track pants and black gloves.
The second man, who spat on the victim, is perceived to be Caucasian in appearance, with facial hair, a balding or shaved head and wearing a brown jacket and dark pants.
The third man who threw a liquid believed to be urine at the victim is described as wearing a bicycle helmet, grey jacket and blue jeans with dark patches.
He was further assaulted by a fourth man at the intersection of Flinders Lane and Queen Street, who threw a drink can at the victim which hit him in the head, just after 12.30pm.
This man is described as wearing a light blue jumper, blue track pants with a white stripe and a light-coloured beanie.
The victim received minor injuries.
Police hold concerns about the unacceptable behaviour and have released images of four men they believe can assist them with their enquiries.
Anyone who witnessed the incident or saw these men is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au