Police are investigating an armed robbery at licenced premises in Melbourne last month.

Investigators have been told a man entered the bathroom at the premises where he confronted another male patron, about 6am on 17 February.

The man demanded cash and produced a metal spike and threatened the victim before stealing his sunglasses.

The offender followed the victim out of the bathroom and once alongside him, punched him in the face.

The victim suffered instant blindness in his right eye and other serious facial injuries.

The offender fled on foot via a rear entrance and walked to a nearby railway station.

Police have released images and CCTV footage of a man who may be able to assist with their investigation.

This man appears to be about 177cm tall, 20 years-old, with a medium to solid build, dark coloured curly hair.

He was wearing a black baseball cap, a white ‘Nena & Pasadena’ muscle top and blue jeans with maroon ‘nmd’ runners.