A man suffered a broken cheekbone after being punched during a robbery in Rockingham Road, Kettering.
The victim, a 26-year-old man, and a friend were approached by three other men while walking along Rockingham Road, near Duke Street, at about 10.45pm on Wednesday, May 21.
After being threatened with a knife, the victim was punched in the face causing a broken cheekbone.
The offenders demanded money and stole cash, jewellery and an iPhone, before making off towards the town centre in a light grey or silver BMW 5 series.
The offenders are described as black, in their late 20s to early 30s, about 6ft 2in and slim build. They all wore dark clothing.
Witnesses to the incident, or anyone with information about it, is asked to call Northamptonshire Police on 101 or Crimestoppers on 0800 555111.