Nobel Peace Prize winner Nadia Murad, a Yazidi who escaped IS and became an outspoken advocate for her community, attended the ceremony in her home village of Kojo to mark the start of exhumations.

The United Nations, which is assisting with the forensic work, says the first opening of a mass grave in the region will help to shed light on the fate those inhabitants killed by IS.

Hundreds of men and women from the village are believed to have been executed by the jihadists when they took over the area in 2014.

The Yazidi people were targeted by the IS jihadists who swept across northern Iraq in 2014 and seized their bastion of Sinjar near the border with Syria.

IS fighters slaughtered thousands of Yazidi men and boys, then abducted women and girls to be abused as sex slaves.

The Kurdish-speaking Yazidis follow an ancient religion rooted in Zoroastrianism, but IS considers them to be "apostates".

The United Nations has said IS's actions could amount to genocide, and is investigating the jihadist group's atrocities across Iraq.

Murad called at Friday's event for Iraq's central authorities and those in the Kurdistan region to "protect the mass graves" so that proof could be found of the "genocide of the Yazidis".

"There will not be reconciliation with the Arab tribes of our region if their dignitaries don't give the names of those who carried out the crimes so they can be judged," she said.

The head of the UN investigative team Karim Khan said the exhumation marked an "important moment" for the probe, with 73 mass graves discovered so far in Sinjar alone.

"The road towards accountability is a long one, and many challenges lay ahead," he said in a statement.

"Notwithstanding this, the spirit of cooperation between the survivor community and the government of Iraq is to be applauded."

IS is currently battling to defend the last shred of its crumbling "caliphate" across the border Syria in the face of Kurdish-led forces backed by an international coalition.