Police believe four armed robberies in the north of the county are linked.
All four robberies involved two men with a knife and machete threatening staff and took place on Monday and Tuesday (January 16/17).
At around 6pm on Monday, two men with face coverings went into the One Stop shop in Brambleside, Kettering with a machete and a knife.
They demanded money but were refused and left empty handed.
At 9.30pm the same evening, two men, also wearing face coverings, and carrying a knife and a machete, went into the One Stop in Churchill Way, Burton Latimer, as reported in the Northants Telegraph.
They took cash and alcohol and made off up Churchill Way.
At 8.30pm on Tuesday evening, two men with face coverings went into the Co-operative Food shop, Occupation Road, Corby, with a machete and knife, and stole cash and alcohol before leaving and making off towards Tansfield Grove.
At 9pm on the same evening, two men wearing face coverings and with a knife and machete demanded cash at the Tesco Express shop, Market Hill, Rothwell.
They left with nothing and ran off up Tresham Street.
Anyone with information about any of these incidents are being urged to contact Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555111.