In figures it calls "staggering", the United Nations says that almost 19,000 civilians have been killed and more than 36,000 wounded in violence in Iraq since the start of 2014.

In a new joint report published on Tuesday, the UN Assistance Mission for Iraq and the Office of the UN High Commissioner for Human Rights listed a large number of atrocities committed by the Islamic State of Iraq and the Levant (ISIL) group.

It also called on the government to do more to stop sectarian violence and help displaced families to return to their homes.

"Even the obscene casualty figures fail to accurately reflect exactly how terribly civilians are suffering in Iraq," UN rights chief Zeid Ra'ad Al Hussein said in a statement on Tuesday.

"The figures capture those who were killed or maimed by overt violence, but countless others have died from the lack of access to basic food, water or medical care."

The UN's figures are based on casualties reported between January 2014 and October 2015.

'Thousands held as slaves'

The joint report highlighted abuses committed by ISIL, saying that about 3,500 people were currently being held as slaves in Iraq by the armed group.

"Those being held are predominantly women and children and come primarily from the Yazidi community, but a number are also from other ethnic and religious minority communities," the UN report said.

No end in sight for Iraq's nights of terror

The report detailed executions by shooting, beheading, bulldozing, burning alive and throwing people off the top of buildings.

"[ISIL] continues to commit systematic and widespread violence and abuses of international human rights law and humanitarian law. These acts may, in some instances, amount to war crimes, crimes against humanity, and possibly genocide," the UN said.

The UN reported that more than 3.2 million people were internally displaced (IDPs) because of violence in the period between January 2014 and October 2015.

"The persistent violence and scale of the displacement continue to impact IDPs’ access to basic services, such as housing, clean water and education," the UN said.

Al Jazeera's Mohammed Jamjoom, reporting from Baghdad, said that more than one million of the internally displaced people were children.

"Sectarian tensions continue to rise and this makes it all the more difficult for displaced people in Iraq," our correspondent said, adding that the UN was pushing for the international community to do more to help the Iraqi government to assist the growing number of homeless families.