Police are investigating five armed robberies and one attempted armed robbery that occurred within two hours of each other in the northern suburbs earlier this morning.

Investigators from the Broadmeadows Embona Task Force believe the same man is responsible for all the robberies which were committed on convenience stores and service stations.

The first armed robbery occurred at 1.25am where the offender, armed with a knife, entered a service station at 1182 Sydney Road, Fawkner and after threatening the attendant, stole an amount of cash.

The next incident, an attempted armed robbery took place at 1.35am where the offender entered a service station at the corner of Stanley Drive and the Hume Highway in Somerton.

At this location the attendant refused to hand over any cash and the man fled in a black Toyota Celica or similar vehicle.

Not wanting to go home empty handed, the man struck a third time at 1.50am, this time targeting a 24hr convenience store at the intersection of Sydney and Murray roads in Coburg where he was handed an amount of cash after threatening the attendant.

The man then travelled to Alphington and at 2.13am hit another convenience store located at 779 Heidelberg Road. As in the previous robberies, the armed man threatened staff and was subsequently handed a small amount of cash before fleeing.

The next location was another convenience store at 4 Union Road, Lower Templestowe, where at 2.45am he struck again using the same method before fleeing on foot on Foote Street, with an amount of cash he took from the till.

Unlucky last was another convenience store at the corner of Keilor and Hoffmans road in Niddrie. At 3.29am the man, still armed with the knife, bailed up the attendant and added a small amount of cash to his ill gotten gains.

Investigators have released an image of a man they believe will be able to assist with their inquiries into these robberies.

The man is described as Caucasian, approx 175cm tall, aged in his mid 20s with short dark hair.

 At the time of the robberies he was wearing a dark coloured top with white horizontal stripes, dark pants and a brown chequered base ball cap.