The man entered the TR News store and demanded cash from a male member of staff at around 7pm on Wednesday.
After taking the money the man left on bicycle with silver rimmed wheels.
The robber is described as 6ft tall, muscular and was wearing a dark coloured coat with lighter coloured hood.
His face was covered and he wore black gloves.
The shop worker was unharmed during the robbery.
Investigating officer, PC William Townsend of Force CID, said: “We are appealing for anyone who may have witnessed this incident or recognises the description of the offender to contact police.
“He left the scene on a push bike, so may have passed members of the public who were out walking around 7pm.”
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