Cambridgeshire police said the incident happened at about 5.30pm in Mayfield Road when the boy was approach by a group of six youths and one member - a girl - shouted abuse at the victim. Another member of the group, a boy, got off his bike and punched the teenager. All of the group then ran off. They were described as white and around 14. The offender was described as wearing a black hooded top. Pc Steve Croft said: This was an unprovoked attack and I would urge anyone with information about this group to contact me. Several people were with the offender and I would urge them to do the right thing and come forward. INFORMATION: Contact Pc Croft on 0345 456 456 4 or Crimestoppers, anonymously, on 0800 555 111.