Islamic State insurgents carried out mass executions, sold women into sex slavery and recruited child fighters, according to a United Nations report that paints a grim picture of the extremist group.

A 40-page report published by the UN on Tuesday details human rights abuses that occurred between July 6 and Sept. 10.

The report, based on 500 interviews with witnesses and surviving victims, was produced by the UN Assistance Mission for Iraq and the UN Human Rights Office.

The UN said that the ongoing armed conflict in Iraq is taking a heavy toll on civilians, despite international humanitarian and human rights laws.

The report catalogued a "range of gross human rights abuses, including murder, physical and sexual assault, robbery, wanton destruction of property, destruction of places of religious or cultural significance, forced conversions, denial of access to basic humanitarian services, and forced expulsion."

Vulnerable groups including minorities, women, children, people with disabilities and the elderly are systematically attacked, the UN said.

"The array of violations and abuses perpetrated by (ISIS) and associated armed groups is staggering, and many of their acts may amount to war crimes or crimes against humanity," UN High Commissioner for Human Rights Zeid Ra'ad al Hussein said.

Gender-based violence

The report claimed that the extremist group treats women "particularly harshly." Female doctors, lawyers, politicians and other professionals have been killed by members of the organization, it said.

Women of different religions are being asked to convert, the report said. Married women who convert are told that their marriages are not recognized under Islamic law, and they are given to ISIS fighters as wives, along with unmarried converted women.

Women who refuse to convert are either given to fighters as wives or trafficked as slaves.

The UN report said that ISIS insurgents in Iraq herded between 450 and 500 women and girls of Yezidi and Christian minority to be given to soldiers in Syria as a reward or to be sold as sex slaves in July and August.

Some of the women are given or sold to young men in Mosul, Iraq and Raqqa, Syria as a means of recruiting them as fighters.

Forced recruitment and use of children

Some children are sent to orphanages, traumatized after watching their parents be killed in front of them, the report said. Some report being sexually assaulted by ISIS fighters during raids.

The UN said it had received numerous reports alleging that ISIS and affiliated groups are actively recruiting children as young as 13 as fighters. Witnesses told the UN they'd seen armed children wearing attire similar to ISIS fighters accompanying patrols. The children were seen carrying weapons, sometimes too big for them to hold up, witnesses said.

On Aug. 5, the UN International Child's Fund (UNICEF) reported that 25,000 children who had fled to Jabal Sinjar were in immediate need of assistance including drinking water and sanitation services. Several died from hunger, dehydration and heat.

Witnesses told the UN that some women are throwing themselves and their children off of mountains in desperation.

Survivors told the UN that ISIS fighters gathered all males older than 10 at a local school and took them outside the boundaries of Khocho village on Aug. 15. As many as 400 males were then killed, the report said.

Mass executions and targeted killings

On Aug. 10, Iraq's former human rights minister Mohammed Shia al-Sudani told media that members of Iraq's Yezidi community had been thrown into mass graves. Some of the victims were women and children who had been buried alive, he said.

According to the report, several mass graves have been found in Sinjar district, Sulaiman Bek, Tawakkul village, Diyala, Baquba and other areas. All the deceased died from gunshot wounds, mostly to the head.

In one instance, survivors told the UN they were confronted by ISIS fighters in Qiniyeh village as they fled their home towns. Reportedly, men, women and children were separated and robbed, then between 70 and 90 men were taken to a ditch, lined up and shot.

There have been reports of extrajudicial killings and summary executions as well, the UN said.

On July 31, 15 men were executed and reportedly hung from lamp posts in Baquba. Some told the UN that the men were part of a campaign of harassment of Sunni residents in the area.

The UN report said that at least 13 members of two displaced families belonging to an unidentified religious group were stopped at an ISIS checkpoint in Kifar al-Haloubi and executed.

Civilian impact

Sunni and Shi'a mosques, Christian churches and monasteries, Yezidi shrines, Kaka'e shrines and other religious sites have been targets of vandalism and bombings.

"(ISIS) has enforced codes of conduct on civilians living within its areas of control, which fundamentally abuse a range of basic human rights protected by international and Iraqi law," the report said.

Among the rights denied are freedom to religious belief, expression, assembly and association.

Villages have been seized, imams have been forced to pledge allegiance and schools have been hit by air strikes.

The UN estimated that at least 8,493 civilians have died in the Iraqi conflict so far this year, and 1.8 million have had to leave their homes.