Iraqi boys aged under 18 are increasingly being used by the militant group as suicide bombers, bomb makers, informants or human shields to protect facilities against US-led air strikes, the UN Committee on the Rights of the Child said.

“We are really deeply concerned at torture and murder of those children, especially those belonging to minorities, but not only from minorities,” committee expert Renate Winter told a news briefing. “The scope of the problem is huge.”

Children from the Yazidi sect or Christian communities, but also Shi’ites and Sunnis, have been victims, she said. “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,” Winter said.

“There was a video placed (online) that showed children at a very young age, approximately eight years of age and younger, to be trained already to become child soldiers.”

IS is a breakaway al-Qaeda group that declared an Islamic caliphate across parts of Syria and Iraq last summer. It has killed thousands and forced hundreds of thousands from their homes, in what the UN has called a reign of terror.

On Tuesday, the group, which is also known as ISIL (Isis), released a video showing a captured Jordanian pilot being burned alive.

The UN body, which reviewed Iraq’s record for the first time since 1998, 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”.

A large number of children have been killed or badly wounded during air strikes or shelling by Iraqi security forces, while others had died of “dehydration, starvation and heat”, it said.

IS has committed “systematic sexual violence”, including “the abduction and sexual enslavement of children”, it said.

“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,” Winter said, giving no details.

The 18 independent experts who worked on the report called on Iraqi authorities to take all necessary measures to “rescue children” under the control of Islamic State and to prosecute perpetrators of crimes.

Meanwhile, Jordanian fighter jets have carried out new air strikes, the military said, a day after the country’s king vowed to wage a “harsh” war against IS militants.