The UN Security Council has approved a resolution directing United Nations investigators to help Iraq collect evidence to build potential war crimes cases against Islamic State (IS) extremists.

The council voted unanimously on September 21 to create an investigative team to help Iraq preserve evidence "that may amount to war crimes, crimes against humanity, and genocide" committed by IS in Iraqi territory liberated from the group's control.

"It's a huge milestone for all of those who've been fighting for justice for victims of crimes committed by ISIS," human rights lawyer Amal Clooney said, using another acronym for the group.

Iraqi Foreign Minister Ibrahim al-Jaafari called it "a victory for justice, a victory for humanity, and a victory for the victims."

IS militants seized parts of Iraq in 2014 and proclaimed it a caliphate under Islamic rule. In Mosul and other captured areas, witnesses say IS carried out mass killings, beheadings, rapes, and other alleged atrocities, some of which it recorded in videos displayed on social media.

U.S.-backed Iraqi forces retook Mosul from the extremists in July, and in the months since, have driven IS from all major urban areas in Iraq, leaving only pockets of control for the extremists, who also seized territory in Syria.

Based on reporting by AP and AFP