NAJAF: The civil war in Syria is widening a rift between top clergy in Iraq and Iran who have taken opposing stands on whether or not to send followers into combat on President Bashar al-Assad's side.
Competition for leadership of the community has intensified since the US-led invasion of 2003 toppled Saddam Hussein, empowering majority through the ballot box and restoring the Iraqi holy city of Najaf to prominence.
In Iran's holy city of Qom, senior clerics, or Marjiiya, have issued fatwas (edicts) enjoining their followers to fight in Syria, where mainly Sunni rebels are fighting to overthrow Assad, whose Alawite sect derives from Shia Islam.
Shia militant leaders fighting in Syria and those in charge of recruitment in Iraq say the number of volunteers has increased significantly since the fatwas were pronounced.
Tehran, Assad's staunchest defender in the region, has drawn on other Shia allies, including Lebanese militia Hezbollah.
Hezbollah's open intervention earlier this year hardened the sectarian tone of a conflict that grew out of a peaceful street uprising against four decades of Assad family rule, and shifted the battlefield tide in the Syrian government's favour.
The Syrian war has polarised Sunnis and Shi'ites across the Middle East but has also spotlighted divisions within each of Islam's two main denominations, putting Qom and Najaf at odds and complicating intra-Shia relations in Iraq.
In Najaf, Grand Ayatollah Ali al-Sistani, who commands unswerving loyalty from most Iraqi Shia and many more worldwide, has refused to sanction fighting in a war he views as political rather than religious.
Despite Sistani's stance, some of Iraq's most influential Shia political parties and militia, who swear allegiance to Iranian Supreme Leader Ayatollah Ali Khamenei, have answered his call to arms and sent their disciples into battle in Syria.
"Those who went to fight in Syria are disobedient," said a senior Shia cleric who runs the office of one of the top four Marjiya in Najaf.