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Mace in Premier Parade, Aylesford was targeted by a man believed to be in his 20s at around 6am.
The suspect demanded cash and cigarettes but fled empty-handed.
The staff member almost became involved in a fight with the intruder before a customer saw him get into a red getaway car and fled the scene.
A worker from Premier Fish Bar, which is on the same parade as the Premier shop, said there are currently three or four police cars parked outside as detectives begin their investigations.
Kent Police has been contacted for a statement.