Iraqi children who fled recent fighting near the city of Mosul prepare to sleep on the ground with their family as they try to enter a temporary displacement camp but are blocked by Kurdish soldiers on July 3, 2014 in Khazair, Iraq. A report by the UN Committee on the Rights of the Child revealed that children are being crucified and buried alive in Iraq. Getty Images

A United Nations watchdog report revealed on Wednesday (4 February) that Islamic State (Isis) has been crucifying and burying abducted Iraqi children alive in a medieval fashion.

After reviewing Iraq's record for the first time since 1998, the UN Committee on the Rights of the Child denounced "the systematic killing of children belonging to religious and ethnic minorities by the so-called Isis, including several cases of mass executions of boys, as well as reports of beheadings, crucifixions of children and burying children alive."

According to the committee report, Iraqi boys under 18 are very commonly being used as suicide bombers, bomb makers, informants and human shields against the US-led air strikes.

"We have had reports of children, especially children who are mentally challenged, who have been used as suicide bombers, most probably without them even understanding," committee expert Renate Winter told a news briefing, reported Reuters.

"We are really deeply concerned at torture and murder of those children, especially those belonging to minorities, but not only from minorities. The scope of the problem is huge."

Winter said children from across Yazidi sect, Christian communities, Shi'ites and Sunnis are amongst the victims.

"Children of minorities have been captured in many places ... sold in the market place with tags, price tags on them, they have been sold as slaves," said Winter.

A total of 18 independent experts reportedly worked on the report and called on Iraqi authorities to "rescue children" from IS and bring to justice the perpetrators.

"There is a duty of a state to protect all its children. The point is just how are they going to do that in such a situation?" said Winter.