An 18-year-old man was robbed of his mobile phone during the early hours of Saturday morning (September 7).
The incident happened sometime between 2.45 and 3.10am at the junction of Park Road and Wood Street in Kettering.
The victim was approached by two men who asked him for the time.
He replied that he did not have the time as his phone was flat. The offenders then grabbed him by the front of his shirt, threatened him with an unknown weapon and stole his phone.
The offenders are both described as black men, aged about 18.
One of the offenders was about 5ft 5in, of medium build, with short cropped hair, wearing a grey hooded top and dark trousers.
The other was around 5ft 8in, of medium build, with short cropped hair, a round face and deep voice.
Witnesses to this incident, or anyone with information, should phone Northamptonshire Police on 101. Alternatively, phone Crimestoppers on 0800 555111.