ABC News: Andrew Griffits

It is believed the 18-year-old victim approached two unknown men at the intersection to ask for the time about 11.30pm on 4 September.

One of the men showed the victim he had a knife in his pocket and demanded he hand over everything he had or he would be stabbed.

The man then head-butted the victim before the two men walked east up Collins Street.

The victim walked to the Melbourne East Police Station where he reported the incident.

The man that allegedly had a knife and assaulted the victim is perceived to be Sudanese, approximately 198cm tall, approximately 20-years-old and was wearing a bomber jacket, red shirt and ‘snap back’ cap.

The second man is perceived to be Caucasian, approximately 188cm tall, approximately 19-years-old and was wearing blue jeans, denim jacket and a ‘stretcher’ earing in his right ear.

Investigators have released an image of two men they believe may be able to assist with their enquiries.

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