ISIS militants have allegedly crucified children, sold them as sex slaves in a market, and, in some cases, even buried kids alive.

Those are just a few of the atrocities mentioned in a new report from the United Nations' Committee on the Rights of the Child. The report touches on an array of problems facing children in Iraq, but paints a particularly harrowing picture of life under ISIS. That picture includes mass killings and almost unimaginable brutality. 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.

Many of the abducted children "are severely traumatized from witnessing the murder of their parents and are subjected to physical and sexual assault." Committee expert Renate Winter also told Reuters that some children are being used as soldiers. Other, mentally challenged children have been used as suicide bombers.