Baghdad: A leading Shiite cleric widely followed by Iraqi militants has issued the first public religious edict permitting Shiites to fight in Syria’s civil war alongside President Bashar Al Assad’s forces.

The fatwa by Iran-based Grand Ayatollah Kazim Al Haeri, one of the mentors of radical Shiite cleric Moqtada Al Sadr, comes as thousands of Shiite fighters mostly from Iraq and Lebanon play a major role in the battles.

The call likely will increase the sectarian tones of the war, which pits overwhelmingly Sunni rebels against members of Al Assad’s Alawite sect, an offshoot of Shiite sect. The situation has worsened with the influx of thousands of Shiite and Sunni foreign fighters.

Al Haeri is based in the holy city of Qom, Iran’s religious capital. Among his followers are many fighters with the feared Shiite militia, Asaib Ahl Al Haq, or Band of the Righteous, an Iranian-backed group that repeatedly attacked US forces in Iraq and says it is sending fighters to Syria. That militia is headed by white-turbaned Shiite cleric Qais Al Khazali, who spent years in US detention but was released after he was handed over to the Iraqi government.

Asked by a follower whether it is legitimate to travel to Syria to fight, Al Haeri replied: “Fighting in Syria is legitimate and those who die are martyrs.”

His comments were posted on his official website. An official at his office confirmed that the comments are authentic.

Asaib Ahl Al Haq currently has about 1,000 fighters in Syria and many others were volunteering to go join the battle, said Ashtar Al Kaabi, an Asaib Ahl Al Haq member who organises sending Shiite fighters from Iraq to Syria. Asked whether the increase is related to Al Haeri’s fatwa, Al Kaabi said: “Yes. This fatwa has had wide effect.”

Over the past year, jihadi groups have begun playing a bigger role in Syria’s war and openly calling for the killing of Shiites and Alawites because of their beliefs.

Al Assad recently said that fighters from more than 80 countries have come to Syria to fight against his forces. The rebels are mainly backed by Saudi Arabia and Turkey, Sunni powerhouses in the Middle East.

The main Western-backed Syrian opposition group, the Syrian National Coalition, claimed recently that Shiite fighters from 14 different factions are fighting alongside government forces in Syria. The coalition said those fighters are brought to Syria with the help of Iraq’s Shiite Prime Minister Nouri Al Maliki, though Iran remains Syria’s strongest ally.

Lebanon’s Iran-backed Shiite Hezbollah also openly joined Al Assad’s forces in May after hiding its participation for months. Since then, the group has helped government forces recapture a string of towns and villages near the Lebanese border.