Arab League chief Nabil al-Arabi denounced on Monday "crimes against humanity" committed by jihadists in Iraq against the minority Yazidi sect, demanding the perpetrators be brought to justice.

Iraqi politicians have warned of the dire plight of Yazidis stranded high up a mountain after Islamic State militants overran their lands.

The jihadists' advances in northern Iraq have also prompted an exodus of Christians.

Arabi "strongly denounced the crimes, killings, dispossession carried out by the terrorist (IS) against civilians and minorities in Iraq that have affected Christians in Mosul and Yazidis," he said in a statement.

Referring to reports of hundreds of Yazidis killed in the jihadist onslaught, Arabi said "these terrorist crimes amount to crimes against humanity that cannot be overlooked."

"The perpetrators must be held accountable and brought to international justice," the statement said.