QOM: Shia and Sunni clerics from about 80 countries gathered in Iran's holy city of Qom on Sunday to develop a strategy to combat extremists, including the Islamic State group that has captured large parts of Iraq and Syria.

Iran has been helping Iraqi, Syrian and Kurdish forces battle the extremist group on the ground while the US-led coalition has been bombing it from the air.

The Islamic State group has massacred hundreds of captured Syrian and Iraqi soldiers, as well as Sunni rivals.

Grand Ayatollah Nasser Makarem Shirazi, the chief organizer of the conference, appealed for consensus among Islam's two main branches, urging all Muslim clerics to work to discredit groups espousing extremism.

“Military attacks against this deviant group (IS) are necessary but insufficient. The roots of their violent ideology must be dried up. This is the job of Muslim scholars, to preach the true, moderate face of Islam and expose the ugly face of IS ideology,” said Shirazi, a prominent Shia cleric who has a large following in Iran and abroad.

Iraq's Foreign Minister Ibrahim al-Jaafari, a Shia, said the Islamic State group is the biggest threat to Islam. “

They were created to undermine Islam and destroy Muslim societies. IS kills both Shia and Sunni Muslims,” he said. Sunni scholar Abdolrahman Sarbazi, who leads Friday prayers in an area of southeastern Iran that is home to many Sunnis, said “Sunni Muslims also condemn the violent practices, which are a threat to humanity.”

Others repeated widely-circulated conspiracy theories holding that the United States and Israel created the Islamic State group to sow discord in the Muslim world.

“IS is a pawn whose job is to deepen divisions among Muslims,” said Mahdi Alizadeh Mousavi, a lower-level Iranian Shia cleric.

Iran is a strong backer of the Lebanese Hezbollah, viewed as a terrorist group in the West, and supports Iraqi Shia militias that rights groups say have abducted and killed scores of Sunni civilians in reprisal attacks.