The United Nations human rights office says Islamic State (IS) militants may have committed genocide against Iraq's Yazidi community as well as crimes against humanity and war crimes against civilians.
In a report, the UN's human rights office called on the UN Security Council to refer the situation to the International Criminal Court at The Hague for prosecution.
The IS group swept through parts of northern Iraq in June, killing hundreds of male members of religious minorities, particularly Yazidis, while enslaving women and forcing small children to convert to Islam.
Hundreds of thousands of people in Iraq fled their homes ahead of the IS advance.
The UN report was based on interviews with more than 100 alleged victims of crimes by IS fighters and witnesses to the crimes against religious minorities, including Shi'a Muslims.
The report added that Iraqi government forces and its militia groups "may have committed some war crimes" fighting against IS forces.