Detectives from Bayside Sexual Offence and Child Abuse Investigation Team are investigating after a woman was sexually assaulted in Patterson Lakes last month.
Investigators have been told a woman was exercising in the Kurrawa Linear Reserve when she observed a man enter the reserve from Colac Court about 9.20am on 30 July.
A short time later the 21-year-old woman observed the man sitting on a bench masturbating.
He approached the victim from behind, grabbed her and attempted to sexually assault her.
She struggled with the man until he fled on foot toward Gladesville Boulevard.
Investigators have released CCTV images of a man who they believe can assist with their enquiries.
He was perceived to be Caucasian in appearance, aged 20 to 25-years-old, about 170cm tall and spoke with a raspy voice.
The man was wearing a black hooded jacket and black tracksuit pants.
Anyone who can identify the man or with any information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au