Staff at Lloyds Bank in Newmarket were threatened with a weapon this afternoon when a man wearing a balaclava entered the building and demanded cash.
Police were called to the bank, on High Street, at around 2.45pm and an investigation is ongoing.
It is not yet clear if any money was stolen in the incident.
The offender is described as wearing a black balaclava and dark coloured jeans.
He ran out of the rear of the bank into Fred Archer Way.
No-one was injured during the incident.
Police are appealing for any witnesses or anyone with information to call Bury CID on 101 quoting crime 217.
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