Iraqi Shiites clash in Basra

The fighting, which Iraqi officials said killed at least 35 people and injured 100, was the most serious sign yet that a cease-fire credited with helping improve security nationwide may be unraveling as groups within the Shiite Muslim majority jockey for position ahead of provincial elections in October.

Explosions and machine-gun fire rocked Basra, where rival political factions, their allied militias and criminal gangs are vying for control of oil exports that generate most of Iraq's government revenue.

Representatives of radical Shiite cleric Muqtada Sadr announced nationwide protests against what they said was the targeting of his followers. The unrest quickly spread to Baghdad, where U.S. and Iraqi officials said armed Shiite militiamen descended on the streets in some neighborhoods and fired a barrage of rockets or mortar rounds at the heavily fortified Green Zone.

The unrest represents an important challenge for an Iraqi government trying to assert control. Many observers view the central government and security forces as weak. Residents in Basra, for example, complain of deteriorating security now that British forces have handed responsibility to local government. In addition, many residents and observers worry that the months leading to the elections will bring increased fighting and lawlessness.

The latest violence was the second time this week that the Green Zone, which houses the U.S. Embassy and Iraqi government offices, took fire from Shiite sections of Baghdad. An auditor for the federal Office of the Special Inspector General for Iraq Reconstruction died Monday of wounds sustained in an attack Sunday, a spokeswoman said.

A U.S. soldier was killed Tuesday when a patrol was attacked with mortar fire in west Baghdad, a military spokesman said. The death raised to 4,001 the number of U.S. military personnel killed since the Iraq war began in 2003, according to the independent website icasualties.org.

Clashes were also reported between members of Sadr's Mahdi Army militia, which waged two major uprisings in 2004, and Iraqi security forces in the southern cities of Kut and Hillah.

Analysts warned that the fighting could spread as the Shiite factions use their influence within Iraq's security forces to weaken their rivals ahead of the Oct. 1 elections.