Police are investigating a terrifying sexual assault on a regional street.

A teenage woman has told police she was walking along Raymond Street, Sale, when she was confronted by a man around 11pm on Saturday night.

The man grabbed her and held an unknown object to her neck before telling her not to scream.

She told police they walked to an area several metres away and she asked him to let her go.

He did, but not before grabbing the woman on the buttock.

The victim told police she saw a car do a u-turn as she ran off and fled the area.

The man is described as being perceived to be Caucasian in appearance, about 178cm tall with a medium build and a short, dark beard.

At the time of the incident he was wearing a black t-shirt with a red and white print, dark pants and a dirty white beanie.

Anyone who has information about the incident or the man’s identity is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.