Sexual Crime Squad detectives are investigating a sexual assault in a Thornbury park last night.
A 32-year-old woman was walking a dog south along Leinster Grove when she noticed a man ahead of her acting suspiciously about 10.30pm.
To avoid the man, she has crossed the road and walked into Mayer Park.
The man approached the victim and asked for her assistance in locating an item he had lost.
When she assisted, the man produced a knife, pushed her to the ground and sexually assaulted her.
The victim managed to grab the knife from the offender and it's believed she stabbed him.
The offender released her and she ran with the dog to seek help from a driver stopped at a set of traffic lights at the intersection of Normanby Avenue and Leinster Grove and police were notified.
The man is perceived to be Caucasian in appearance, aged in his early 20s, with a medium height, brown hair and was wearing loose pants and a hoodie.
It's believed the man may have sustained a stab wound and may seek medical treatment.
Anyone with dash cam footage who travelled along either Normanby Avenue or Leinster Grove between 9.30-10.30pm is urged to come forward.
Any witnesses or anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.
