Staff at Betfred Newmarket last night locked themselves into a back room and set off an emergency alarm after a man wearing a mask entered the store holding a knife.
The incident took place at Betfred in Valley Way and police were called at around 8.55pm.
The two members of staff – a man and a woman - were the only people in the shop at the time.
The man is described as around 5ft 7ins tall, of thin build, wearing a black woollen hat, a black hooded top, black jogging bottoms or similar, and a white mask, and was carrying a black drawstring bag.
He left the shop empty handed after failing in his attempt to get over the counter.
No one was hurt but the staff members have been left shaken following the incident.
Police are asking anyone who may have been in the area around this time or anyone with information about the male involved to contact detectives at west Suffolk CID by calling Suffolk Police on 101, quoting crime number 12735. Alternatively you can call Crimestoppers, anonymously if required, on 0800 555 111.
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