Police are investigating an armed robbery at a milk bar in Dandenong on Saturday (15 July).

A man entered the business on Hemmings Street about 12.40pm and approached the counter.

Staff began to offer assistance to the man who then threatened them with a knife and demanded cash.

The offender was confronted by a third staff member, causing him to retreat and flee from the store.

It is believed he ran in a northerly direction along Weller Street and did not manage to steal anything.

No one was physically injured during the incident.

The man involved in the incident is perceived to be aged in his mid-30s to early-40s, with a slim build, and a tanned complexion. He was wearing a dark jumper with white lines around the cuffs and knee length shorts with white stripes part way down the side.

It is also believed the man had a mask or covering to conceal half of his face.

Investigators have released CCTV vision of a man that may be able to assist with their enquiries.