A 14-year-old boy was pushed up against a wall and threatened with a knife before being robbed of his iPod.
The boy was approached by three men in Birds Hill Road, near Tyes Court, in Lings, Northampton.
The men, who were all dressed in black tracksuits and wearing scarfs to cover their faces, threatened the boy with a knife and pushed him against a wall.
They then demanded his property and stole his Apple iPod.
A spokesman for Northamptonshire Police said: “The victim was not injured but was left very shaken.”
Two of the offenders are described as being black with a slim build and the other was white with a stocky build. He was wearing white-framed glasses.
One of the men was carrying a small Nike bag. All of them were in their late teens to early twenties.
The robbery happened on Tuesday, November 3 at about 4pm.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.