Darebin Crime Investigation Unit detectives have released CCTV vision after a man armed with a firearm and wearing a Fedora hat robbed a supermarket in Preston on Tuesday afternoon.

Investigators have been the offender entered the supermarket on Cramer Street about 3.40pm and approached a female staff member.

The offender pointed the firearm towards the employee and pushed it into her stomach, making demands for cash.

During this time, a number of other staff members approached the man, who then pointed the firearm towards them.

He stole an amount of cash from one of the registers and fled on foot.

Two male staff members chased the offender out of the store and into the car park.

The man was last seen running down a laneway behind the shop on High Street, near the intersection of Cramer Street.

Police have released the below CCTV images of a man who they believe may be able to assist with their enquiries.

The man is described as being Caucasian, aged between 30 and 40 years, approximately 180cm tall and solid build.

He was wearing a beige jumper, a black skivvy style top, jeans and black shoes.

The offender was also wearing a beige Fedora style hat with a black band.