A man entered the Co-Op store in Blackburn Road before picking up a case of lager and approaching the checkout at around 8.25pm on Monday (June 20).
After placing the case of lager on the till area, the man produced a weapon before threatening a member of staff.
He then forced his way into the till area before demanding money and taking an “undisclosed amount of cash”.
The suspect is described as a white male, approximately 6ft tall and of medium build.
Police said he was wearing a black Nike Hoodie, black shorts and a black baseball cap.
Anyone with information can email [email protected] or call 101, quoting log number 1361 of June 20.
Independent charity Crimestoppers can also be contacted anonymously on 0800 555 111 or online at https://crimestoppers-uk.org/.