Dandenong Embona Task Force detectives are appealing for public assistance after three businesses were robbed in a three week period last month.

The first incident was at a business on Herbert Street on 3 September about 7.40am.

A man entered the store and placed a bottle of alcohol on the counter before producing a knife from a blue shopping bag and demanding cash.

The staff member complied and the man fled on foot west toward Stud Road.

The second incident was at a business on Ross Street on 14 September about 8.15pm.

A man entered the store and placed a drink from the fridge on the counter before lifting up his top revealing a knife in his pants and demanding money.

The staff members retreated to the back of the store and the man helped himself to the till.

The third incident occurred at the same store on Ross Street on 17 September about 8.30pm.

On this occasion the man entered the store and approached the counter with a knife and pink shopping bag and demanded money.

The staff member complied before chasing the man down Ann Street toward Stud Road for approximately 100 meters.

No one was injured during the incidents but the same man is believed to be involved in each armed robbery.

The man is perceived to be Caucasian or Middle Eastern in appearance, aged in his late teens to early 20s, thin build, approximately 175cm tall and has a pointy nose.

Investigators have released an image of a man they believe may be able to assist with their enquiries.