Detectives from Port Phillip Crime Investigation Unit are appealing for information following an armed robbery in Port Melbourne.

Investigators have been told a man entered a juice bar on Bay Street around 2.15pm on Sunday and ordered a drink.

He handed the attendant a note and when the till was opened he put his hand in his pocket and told the attendant that he had a gun.

The offender then reached over and stole the cash draw before leaving the store and heading south along Bay Street.

He is perceived to be Caucasian, about 182cm tall with light brown hair.

At the time of the offence he was wearing sunglasses, a hat, dark pants and jacket.

Police have released images and CCTV of a man that they believe may be able to assist with their enquires.