The man, wearing a balaclava entered the Total garage in Melton Road on Friday night and lifted up his clothes to reveal the handle of a gun.
Police said no shots were fired and no-one was injured in the robbery.
The man fled towards the centre of Melton. Armed police and police dog handlers were called to the scene, but failed to find the him.
He is described as between 5ft 11in and 6ft 2in tall, with a thin build.
He was wearing jeans and a grey or navy blue hooded top.
Any witnesses or anyone with information is asked to call Suffolk Police.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~35~RS~)