REUTERS - ISIS militants committed genocide against Iraq's Yazidis in the north of the country and carried out crimes against humanity, ethnic cleansing, and war crimes against other minorities, the U.S. Holocaust Memorial Museum said on Thursday.

The crimes were committed against Christian, Yazidi, Turkmen, Shabak, Sabaean-Mandaean, and Kaka'i people in Nineveh province between June and August 2014, found a report by the museum's Simon-Skjodt Center for the Prevention of Genocide.

"We believe Islamic State has been and is perpetrating genocide against the Yazidi people," the report said. "Islamic State's stated intent and patterns of violence against Shia Shabak and Shia Turkmen also raise concerns about the commission and risk of genocide against these groups."

The United Nations said in March that Islamic State may have committed genocide in trying to wipe out the Yazidi minority and urged the UN Security Council to refer the issue to the International Criminal Court for prosecution.

Islamic State militants have seized swathes of territory in Iraq and Syria. Both states are not members of the Hague-based court so its prosecutor is unable to open an investigation unless a referral is made by the 15-member Security Council.

A U.S.-led coalition has been bombing Islamic State targets in Syria and Iraq for more than a year.

Islamic State militants consider the Yazidis to be devil-worshippers. The Yazidi faith has elements of Christianity, Zoroastrianism and Islam. Most of the Yazidi population, numbering around half a million, remains displaced in camps inside the autonomous entity in Iraq's north known as Kurdistan.

Of around 5,000 Yazidi men and women captured by the militants in the summer of 2014, some 2,000 have managed to escape or been smuggled out of Islamic State's self-proclaimed caliphate, activists say. The rest remain in captivity.

"Men, women, and children who were kidnapped and are still being held by Islamic State continue to be the victims of atrocity crimes. Their release must be a priority," said the museum report.

The 1948 UN Convention on the Prevention and Punishment of the Crime of Genocide defines genocide as intent to destroy in whole or in part a national, ethnical, racial or religious group.

The convention says this can be done by killing members, causing serious bodily or mental harm to members, deliberately inflicting conditions on the group calculated to bring about its physical destruction, preventing births within the group or forcibly transferring children of the group to another group.