A high-vis wearing man who was seen masturbating in front of an empty playground in Melbourne's north continued the vile act, despite the attention of a passer-by.

The man was seen in the park near the Epping railway station in Grand Parade about 6.50am on Saturday.

An image of a man police wish to speak to.

A woman walking to the station said the man was masturbating while holding a plastic bag and appeared unperturbed by her presence.

The man is described as Asian, about 165cm tall, with a medium build and black, fluffy hair. He was wearing a blue and yellow high visibility jacket and carrying a plastic bag.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or via crimestoppersvic.com.au