The United Nations revealed that ISIS has stepped up the use of children in its bloody campaign of terror, subjecting them horrors that include putting price tags on them to sell as slaves. A report released this week focused on children in Iraq, as well as the responsibility of that nation's government for ensuring the safety and security of young civilians in the conflict. But it certainly doesn't preclude similar things happening in Syria, where ISIS is also entrenched and also has been blamed for various atrocities. In reference to Iraq, at least, the U.N. report found that the terrorist group is resorting more and more to brutal acts such as enslaving, raping, beheading, crucifying and burying people alive. Some of those affected are children. Here are some of the more horrific allegations: ISIS has beheaded and crucified children. Children have been buried alive. There have been "several cases of mass executions of boys." Militants have attached price tags to women and children, then sold them as sex slaves in "markets." Children have been sexually assaulted in makeshift prisons. Parents have been forced to give up their children to ISIS or watch them die. 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 U.S.-led air strikes, the U.N. 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 told Reuters. "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." "We have had reports of children, especially children that are mentally challenged, who have been used as suicide bombers, most probably without them even understanding what has happened or what they have to expect," said Winter Some as young as age 8 are getting training to become soldiers, she said. "Children of minorities have been captured in places where the so-called ISIL has its strength, have been sold in market with tags, price tags on them, have been sold as slaves," Winter said. Yazidi children haven't fared much better at the hands of ISIS. An earlier U.N. report described how militants rounded up all Yazidi males "older than 10 years of age at the local school, took them outside the village by pickup trucks, and shot them. The terror group printed a pamphlet last fall, then distributed it in Mosul in December, entitled "Questions and Answers on Female Slaves and their Freedom." It spells out rationales for having sex with prepubescent girls and generally capturing those who are "nonbelievers," i.e. they don't subscribe to ISIS's extreme take on Islam. As such, the ISIS document claims, "It is permissible to buy, sell or give as a gift female captives and slaves, for they are merely property." The U.N. report wasn't just critical of ISIS. It also urged the Iraqi government -- which, along with neighboring Syria, is fighting the Islamist extremist group -- to do more to protect children, saying the Iraqi forces are contributing to the problem. A "very large number of children" have been killed and severely injured by airstrikes, shelling and military operations by Iraqi forces, the report said. ISIS has featured children as fighters before, calling them the "cubs of the caliphate" (the adult jihadis call each other "lions") and has encouraged foreign fighters to bring their families. It has taken over schools to indoctrinate children. Human Rights Watch claims ISIS and other extremist groups "have specifically recruited children through free schooling campaigns that include weapons training and have given them dangerous tasks, including suicide bombing missions."