Photo: vicpolicenews.com.au

Police have been told the 15-year-old boy was walking through a park near the Harrington Square shopping strip at about 9.20am.

The teen then saw a man standing on a small grassy area near a residential fence.

He was holding a phone in front of him with one hand, whilst masturbating.

He then left the area.

The man is perceived to be Caucasian in appearance, approximately 170cm tall, aged in his 30s, with a medium build and short hair.

He was wearing a black hooded jumper with a white motif on the back, brown shorts and work boots.

Investigators have released CCTV and a computer generated image of a man that may be able to assist with their enquiries.

Anyone with information or who witnessed the wilful and obscene exposure is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.