Photo: vicpolicenews.com.au

The incident took place in Brookfield as the 20-year-old victim walked along Blue Gum Drive at 7.30pm on Sunday 6 November.

The victim told investigators that he was walking along the footpath when he was approached by the offender riding a push bike.

The offender demanded that the victim hand over his mobile phone.

When the victim refused, the offender produced a small flick knife and threatened to stab him.

The victim ran from the scene and alerted police.

The offender is perceived to be of African appearance, aged in his late teens, with a thin build and short dark hair.

Investigators have released computer-generated images of a similar knife produced in the incident and of a youth they believe can assist with enquiry.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or file a confidential report at www crimestoppersvic.com.au.