A robbery took place in the alleyway linking Halse Road and Burwell Hill in Brackley.
The victim was with a friend when he was approached by two boys, one of whom demanded money and cigarettes.
The victim refused and a scuffle ensued.
The offenders involved in the attack, between 9.20pm and 9.40pm on Friday, were described as white, skinny and aged about 16.
One was 5ft 3in tall, with cropped light brown/blonde hair, wearing a grey hooded top and blue jeans.
The other was 5ft 4in tall, with cropped dark brown hair, wearing an army-style jacket and blue jeans.
Witnesses to this incident, or anyone with information, should call Northamptonshire Police on 03000 111 222, or information can be given anonymously to Crimestoppers on 0800 555 111.
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