Armed Crime Squad detectives have released images of two men they wish to speak to following a robbery outside a bank in Broadmeadows in May.

Investigators have been told the man carrying a back pack attended a shopping centre on Pascoe Vale Road about 4.30pm on Monday 2 May.

It is believed the offender approached the victim outside the shopping centre, making demands to hand over the bag.

He then produced a firearm and the victim handed over the bag containing a substantial amount of money.

The offender fled the scene, returning to a late model silver Mercedes.

The car was later found burnt out in an industrial area on Clifford Road in Somerton about 8pm that night.

It is believed a grey 2009 Lexus sedan, registration 1GZ 1BJ was in the same Somerton area about 8pm, around the time the Mercedes was burnt out.

Detectives have released facial composite images of two men that may be able to assist with their enquiries.

The men are believed to have been in Munro Street, in the vicinity of Sydney Road in Coburg, about 4pm, which was approximately 30 minutes prior to the robbery.