“All communities stand together against hate and we would ask anyone with any information to come forward immediately,” DS Blamires added.
The boy’s friends escaped the attack and suffered only minor injuries.
Islamic State fighters have captured, enslaved and sold Yazidi women and children, and claim the act is justified in Islam to prevent men from feeling "tempted" by other, non-enslaved women.
According to a piece in the group's full-colour magazine, which is published in English and evidently aimed at a Western audience, confirms the long-rumoured atrocities committed by the group in Iraq, where Yazidi women have reported being kidnapped, sold for a few dollars and repeatedly raped.
The latest issue of Dabiq magazine released on Sunday stated, "the enslaved Yazidi families are now sold by the Islamic State soldiers." It added, "the Yazidi women and children were then divided according to the Sharia amongst the fighters of the Islamic State who participated in the Sinjar operations." Anyone opposing slavery in such circumstances is not a Muslim, the piece says.
"Enslaving the families of the kuffār [non-believers] and taking their women as concubines is a firmly established aspect of the Sharia that if one were to deny or mock, he would be denying or mocking the verses of the Qur'an...
He encouraged witnesses and bystanders who came to aid of the boy to contact the police.