A man was forced to hand over cash after being threatened with a knife in Gainsborough Road, Corby, in the early hours of Monday.
The 20-year-old victim was walking along a grassy area at the back of the site of the old Pluto pub when he was approached by two men.
The men threatened him with a knife and demanded he hand over cash.
The incident happened between 12.30am and 12.45am.
One of the offenders is described as tall, with ginger hair, and he had a distinctive mole on his face.
Police are also appealing for witnesses to a knifepoint robbery in Thoroughsale Wood, Woodnewton Way, Corby, between 1.45pm and 2.45pm last Friday.
The victim was walking through the wood when he was grabbed from behind and restrained.
A second offender then threatened the victim with a knife and demanded he hand over money, which he did.
The offender then put the knife to the victim’s face causing him to hand over his mobile phone and medication.
One of the offenders wore a black jacket, blue jeans, white trainers and a white baseball cap with a ‘New York’ motif on it.
Anyone with information about either incident, which police are not currently linking, is asked to call Northamptonshire Police on 101 or information can be given anonymously to Crimestoppers on 0800 555111.