Whittlesea Crime Investigation Unit detectives are appealing for witnesses following an armed robbery at an electronics store in Thomastown last month.

The incident happened at the Dalton Road store on Saturday, 6 June at 2.20pm.

Police have been told a man entered the store and walked around the aisles before stopping at a display of laptop computers.

The man took a box cutter, or possibly a knife, from his pocket and cut the security cable affixed to one of the computers.

With the computer in his hands, the man ran towards the store exit.

A male staff member attempted to stop the robber but backed off when he was threatened.

The man is described as being aged in his late teens to early 20s, with dark hair and a medium build.

At the time of the offence he was wearing a fluro orange and blue high visibility jacket.