Three teenagers were robbed at knifepoint by two masked men.
The three teenage boys were sitting on the benches of the basketball courts at the back of Bondfield Avenue, Northampton, when they were approached by two white men, in their late teens or early twenties, wearing scarves around their faces.
The men threatened the three victims with a kitchen knife and demanded they hand over their mobile phone and money.
One of the victims was then punched in the face several times and his phone was stolen.
One of the offenders was around 5ft 8ins and was wearing a grey hooded top and bottoms, black gloves and a black scarf around his face.
The other offender was wearing black gloves and a black scarf around his face.
The incident happened between 9.30pm and 10.15pm on Thursday, June 21.
Witnesses, or anyone with information, can call Northamptonshire Police on 101 or Crimestoppers on 0800 555 111.