Photo: Mirage News

Investigators have been told an unknown man grabbed an 18-year-old woman before attempting to drag her into the parkland at Malcolm Creek Park about 5.40pm.

The victim screamed alerting a passer-by who came and intervened causing the offender to flee.

The man is described as being Caucasian in appearance, aged in his 20s with a thin build, about 183cm tall with dirty brown/blond hair.

He was wearing a black baseball cap and a white t-shirt.

The investigation is ongoing.

Police are urging anyone who may have witnessed this incident or seen suspicious behaviour in the area to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au.