Geelong Crime Investigation Unit detectives are appealing for public assistance following an armed robbery at a fast food restaurant in Corio on 13 June.

A lone male offender armed with a knife entered the restaurant shortly after 7pm and made demands for money from the staff.

The man is described as Caucasian, heavy build and 182cm tall and was wearing a light grey hooded tracksuit top and pants, black runners and had his face covered.

The man stole a substantial amount of cash before leaving the premises on foot.

He was last seen running west across Princes Highway towards Rosewall Estate.

Investigators have released images of a man they believe may be able to assist with enquiries.