Nearly 19,000 civilians were killed in Iraq during the 21-month period between January 2014 and October 2015, a toll that United Nations' representatives are calling "staggering" in a new report released Tuesday.

The U.N. report outlines the severe and extensive impact that Iraq's ongoing conflict is having on its civilian population, reports CNN.

In the 21-month period, at least 18,802 civilians were killed, about half of them in Baghdad alone. Another 36,245 were wounded. An estimated 3.2 million people were internally displaced, including a million school-aged children.

Of the total number of casualties, at least 3,855 civilians were killed and 7,056 wounded between May 1 and Oct. 31 last year.

The actual figures could be much higher, the report states.

Additionally, U. N. representatives accuse the so-called 'Islamic State of Iraq and the Levant' (ISIL) of committing systematic and widespread violence, including holding some 3,500 mainly women and children as slaves, reports BBC News.

The report, compiled by the UN Assistance Mission for Iraq (UNAMI) and the Office of the High Commissioner for Human Rights (OHCHR), is based largely on testimony obtained directly from the victims, survivors or witnesses of violations of international human rights or international humanitarian law, including interviews with internally displaced people.

ISIL continues to commit acts that in some instances, may amount to war crimes, crimes against humanity, and possibly genocide, the report states.

The report details numerous examples of killings by ISIL in gruesome public spectacles, including by shooting, beheading, bulldozing, burning alive and throwing people off the top of buildings. There are also reports of the murder of child soldiers who fled fighting on the frontlines in Anbar. Information received and verified suggests that between 800 and 900 children in Mosul had been abducted by ISIL for religious education and military training.

The discovery of a number of mass graves is documented in the report, including in areas regained by the government from ISIL control, as well as mass graves from the time of Saddam Hussein. One of the mass graves uncovered reportedly contains 377 corpses, including women and children apparently killed during the 1991 Shi'a uprisings against Saddam Hussein in the east of Basra.

Special Representative of the UN Secretary-General for Iraq, Ján Kubiš, said he calls on the international community to enhance its support to the government of Iraq's humanitarian, stabilization and reconstruction efforts in areas liberated from ISIL, so that all Iraqis displaced by violence can return to their homes in safety and in dignity and that affected communities can be reestablished in their places of origin."

"I urge the government to use all means to ensure law and order, necessary for the voluntary return of IDPs to their place of origin - a task of primary importance given the recent wave of violence and killings, often of sectarian nature, notably in Diyala and Baghdad," Kubiš said.