A woman dancing with friends at a bar in Melbourne's inner north last month was sexually assaulted by a stranger, police say.

The 19-year-old was spending a night out with friends at a Sydney Road bar in Brunswick on April 28. About 3am, a man unknown to the woman walked up behind her and indecently assaulted her, a police spokeswoman said.

Police wish to speak to this man in relation to a sexual assault at a Brunswick bar. Credit:Courtesy Victoria Police

Police have released images of the man they believe can help their investigation.

He is believed to be in his mid 20s, of slim build and with an Indian accent. The man is believed to be about 170 centimetres tall and was carrying a backpack at the time.

Anyone with information is asked to phone Crime Stoppers on 1800 333 000.