Knox Sexual Offence and Child Abuse Investigation Team detectives are appealing for information after a woman was sexually assaulted in a car park in Yarra Glen.

The woman, who is aged in her 20s, was pushing a trolley in the car park behind the Bell Street shopping centre about 8.45pm on Sunday, March 4.

A person then came up behind her, grabbed her around the waist and then put their hand down her pants.

The victim told the person to stop and they ran off.

The woman, who was not physically injured during the incident, then contacted police to report the matter.

Detectives are appealing for anyone who might have witnessed the incident or noticed any suspicious activity in the area around the time.

Police are also keen to speak to a person who was riding a bike nearby at the time of the incident who may have witnessed what occurred.

Anyone with any information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report to www.crimestoppersvic.com.au