Last Updated Jan 19, 2016 3:25 PM EST
BAGHDAD -- A U.N. report released Tuesday says at least 18,802 civilians in Iraq were killed and another 36,245 wounded between Jan. 1, 2014 and Oct. 31, 2015.
The reports calls the civilian death toll "staggering" and details killings by the Islamic State of Iraq and Syria (ISIS) including by shooting, beheading, bulldozing, burning alive and throwing people off of buildings.
The report also said ISIS is believed to currently be holding approximately 3,500 people captive as slaves.
"Those being held are predominantly women and children and come primarily from the Yezidi community, but a number are also from other ethnic and religious minority communities," said the report, issued jointly by the U.N.'s Assistance Mission for Iraq and the global body's human rights office.
It said the crimes committed by ISIS may "in some instances, amount to war crimes, crimes against humanity, and possibly genocide."
ISIS swept across northern and western Iraq in the summer of 2014 plunging the country into its worst political and security crisis since the withdrawal of U.S. troops in 2011.
"That civilians are caught in the crosshairs of ISIS is not new, but the U.N. human rights agency report released Tuesday says that the staggering number of civilians who died in Iraq in the past two years were killed by gunfire, beheading, bulldozing, and by being burnt alive and thrown off buildings by ISIS -- a grim reality check on the increase in violence since U.S. troops withdrew four years ago," CBS News' Pamela Falk reported from the U.N. "U.N. officials fear that the increase in ISIS forces in Iraq will undermine the peace efforts in neighboring Syria and that the fight against ISIS in both countries is now an urgent humanitarian crisis."
"The U.N. report says that despite the steady losses to pro-government forces, ISIS continues to kill, maim and displace Iraqi civilians and that mass graves have been found across the country. It also calls on the international community and the Security Council to provide support to the government of Iraq for security and humanitarian needs. "