ROME, Aug 12 (Reuters) - The Vatican called on Muslim religious leaders on Tuesday to condemn "unspeakable criminal acts" by Islamic State militants who have taken a series of cities in northern Iraq, forcing tens of thousands of Christians and Yazidis to flee their homes.
"No cause, and certainly no religion, can justify such barbarity," the Vatican's Pontifical Council for Interreligious Dialogue, an office set up to promote contact with other faiths, said in a statement.
It said the plight of Christians, members of the ancient Yazidi sect and other religious and ethnic minorities in Iraq required "a clear and courageous stance on the part of religious leaders, especially Muslims".
"All must be unanimous in condemning unequivocally these crimes and in denouncing the use of religion to justify them," it said. "If not, what credibility will religions, their followers and their leaders have?"
The rapid advance of the Sunni jihadists of Islamic State and the brutal treatment meted out to Shi'ites as well as local Christians and Yazidis has drawn a horrified reaction in western countries and prompted the United States to launch limited air strikes against the militants.
The Vatican's call came as Egypt's top religious authority, Grand Mufti Shawqi Allam, condemned Islamic State as a corrupt, extremist organisation that is damaging Islam.
Pope Francis, who leaves for a visit to Korea on Wednesday, has repeatedly condemned the violence in Iraq over the past few days, declaring on Sunday that it "deeply offends God and humanity."
Islamic State, which sees Shi'ites as heretics who deserve death, has seized a series of towns in northern Iraq, in a sweeping advance that has left the Iraqi government reeling and prompted tens of thousands to flee.
The group has declared religious rule in a caliphate straddling Syria and Iraq. It has offered both local Christians and members of the ancient Yazidi sect, whom it calls "devil worshippers", the choice between conversion to Islam and death. (Reporting by James Mackenzie Editing by Jeremy Gaunt.)