A young woman was allegedly sexually assaulted in Melbourne’s CBD before she was hit in the face and left concussed.

The 20-year-old was with her friends walking along Lonsdale Street near the intersection of King Street at 5am on May 8.

The group were then approached by a number of men they did not know.

One of the men then allegedly sexually assaulted the victim and groped her bottom.

After the alleged assault, an altercation broke out between the victim and her group of friends and the other men.

During the altercation, the victim was struck in the face.

She was taken to hospital with bruising and a concussion.

The group of men left the scene after the incident towards Lonsdale Street and police have released an image of a man they believe can assist with their inquiries.

He is perceived to be of Pacific Islander/ Maori appearance with shoulder-length hair in dreadlock type curls.

He was wearing a light-blue T-shirt, faded blue jeans and had a beanie tucked into his pants.

Anyone with information is urged to contact police.