Mernda Sexual Offence and Child Abuse Investigation Team detectives are seeking assistance from the public following three incidents at parks in Mill Park and Lalor in April and June.

Investigators have been told a woman was walking alone on a football oval at Lalor Reserve when she observed an unknown man expose himself and perform a lewd act on 15 April around 12.50 pm.

Two other women have come forward to police to report similar incidents at WA Smith Reserve in Lalor around 10.50 am on 7 June, and at Sycamore Reserve in Mill Park around 3.50 pm on 13 June.

The man is described as being of South-Asian appearance, approximately 160cm tall, with a solid build and a dark-coloured beard.

Investigators believe the three incidents are linked and have released a computer-generated image of a man who may be able to assist with their enquiries.

Anyone with information that could assist police is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.