The United Nations says the Islamic State group is systematically killing, torturing and raping children and families of minority groups in Iraq, and it is calling on government forces there to do more to protect them.

In a report issued Wednesday in Geneva, the U.N. Committee on the Rights of the Child said it has received reports of "several cases of mass executions of boys, as well as reports of beheadings, crucifixions of children and burying children alive."

Iraq's military has been struggling in its fight against Islamic State, and the government has pleaded repeatedly for more weapons and training.

Still, the U.N. agency urged that more be done, saying Iraq needs to "take all necessary actions to ensure the safety and protection of children and their families."