A man armed with a hand gun and wearing a balaclava threatened a female shop assistant before making off with a small amount of cash.
The incident happened at the Premier store, in Rodham Terrace, Stanley, at about 9.15pm on Saturday.
The victim was shaken but unhurt.
Witnesses are asked to call Durham Police on 101 or via Crimestoppers anonymously on 0800-555111.
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