BAGHDAD - Gunmen assassinated a top aide of anti-American leader Muqtada al-Sadr on Friday, sharpening a Shiite power struggle that has already triggered fighting between the cleric's followers and the U.S.-backed Iraqi government.
Riyadh al-Nouri, director of al-Sadr's office in Najaf, was gunned down by an unknown number assailants near his home after returning from prayer services, police and Sadrist officials said.
Al-Sadr blamed the Americans and their Iraqi allies for the killing but called for calm - presumably to avoid a showdown at a time his Mahdi Army militia is under pressure by Iraqi and U.S.-led forces in Baghdad and southern Iraq.
Prime Minister Nouri al-Maliki, also a Shiite, condemned 'this savage crime' and ordered an investigation 'to pursue and arrest the killers.' But many of the 5,000 people who attended al-Nouri's funeral later Friday in Najaf chanted 'al-Maliki is the enemy of God' as they shouted slogans against al-Sadr's Shiite political rivals.
Authorities declared a curfew in Najaf, the world's premier Shiite theological center 100 miles south of Baghdad. Security forces took to the streets in several major cities across the Shiite south. A curfew was also imposed in Hillah, where government troops clashed with al-Sadr's militia last month.
The assassination of such an influential Sadrist figure is likely to increase tension between al-Sadr's movement and the Shiite-led government.
Several prominent Sadrists described al-Nouri as a voice of moderation within the movement, arguing against an armed confrontation with the Americans and al-Sadr's Shiite rivals. He had also opposed a decision by the Sadrists last year to withdraw from al-Maliki's government.
Al-Nouri, 41, was one of al-Sadr's closest aides. Al-Nouri's sister is married to one of al-Sadr's brothers. As director of the Najaf office, al-Nouri was al-Sadr's representative in the world's most prestigious center of Shiite learning.
Al-Nouri and another top al-Sadr lieutenant, Sheik Mustafa al-Yacoubi, were detained by American soldiers in May 2004 in the killing a year earlier of a moderate Shiite cleric, Sheik Abdul-Majid al-Khoei, in Najaf shortly after the U.S.-led invasion of Iraq.
An arrest warrant was issued for al-Sadr himself but was never served. The warrant and the closing by U.S. authorities of al-Sadr's newspaper triggered massive uprisings that engulfed Shiite areas of central and southern Iraq.
Al-Nouri and al-Yacoubi were freed in 2005 as part of an agreement to end the Sadrist rebellion, which claimed several thousand lives.
Tension between al-Sadr and other Shiite parties exploded into violence last month when al-Maliki launched an ill-planned offensive against Shiite militias and gangs in Basra, Iraq's second largest city.
The offensive faltered after al-Sadr's militia launched attacks throughout the south and in Baghdad, where militants showered the U.S.-controlled Green Zone with rockets and mortars, killing four Americans.
Clashes have continued in Baghdad and Basra, despite al-Sadr's order March 30 for his militiamen to stand down under a deal brokered in Iran.