Detectives from the Armed Crime Squad have released CCTV following an attempted armed robbery and armed robbery in Carlton and Clifton Hill earlier this year, Victoria Police say.
CCTV footage shows the offender entering a service station on Elgin Street at about 12:35pm on 4 August.
The unidentified man was armed with a large knife and made demands for money.
The attendant activated the security system and the male left the scene empty handed on a bicycle.
On the same day at about 1:45pm the same unidentified male entered a post office on Queens Parade, Clifton Hill.
Armed with the large knife the offender demanded cash.
Employees complied with his demands and handed over an amount of money before the offender decamped on a bicycle.
The offender was wearing a white hooded top with a black and green motif on the front, blue jeans; black gloves a black balaclava and a silver bicycle helmet.
Anyone who has information is urged to Crime Stoppers.
