The incident happened at commercial premises in the Suffolk Road area yesterday afternoon, Sunday, December 2.
Detective Sergeant McPhillips said: “We received a report around 3:30pm that a man had entered a shop, grabbed a staff member and threatened them with a knife.
“The suspect – described as being approximately 6′ tall, of medium build, aged in his 30s and wearing a red coat, dark-coloured bottoms and a monkey hat – then fled with a sum of money and cigarettes.
“This was a frightening ordeal for this staff member who was doing their job. Thankfully, they were not physically injured, however they have been left badly shaken by this despicable act.
“Police subsequently arrested a 31-year-old man on suspicion of robbery and possession of an offensive weapon with intent to commit an indictable act. He has since been released on bail pending further enquiries.
“I want to appeal to anyone who was in the Suffolk Road area shortly before or around the time was incident was reported to us and saw what happened to get in touch.
“I would also like to hear from anyone who believes they may have seen a man matching the description of the suspect running from the scene, or who captured him on their dashcam footage to get in touch.
“If you have information which you believe may assist our investigation call detectives at Musgrave Police Station on the non emergency number 101, quoting reference number 892 of 02/12/18.”
Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.