A man with a knife tucked in his trousers threatened shop workers in Fulwood before running off.
Around 10.45pm at the One Stop in Black Bull Lane a man entered the shop on Tuesday 19 June.
He spoke to two shop workers before making demands for money and showing a knife he had tucked into his trousers.
Preston Police say he made off on foot with a small amount of coins from the till.
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The man was wearing a black North Face jacket, black jeans and black Nike trainers.
No one was hurt in the incident.
PC Richard Shires of Preston Police, said: “This has been a frightening experience for the shop workers and we’re working to establish who is responsible. I’m appealing to anyone who recognises the man in the CCTV, or saw anything suspicious in the area to come forward and speak to us immediately.”
Anyone with information is asked to ring 101 quoting crime reference SA1812424.