BAGHDAD -- Gunmen killed an aide to Ayatollah Ali al-Sistani in the southern city of Basra, police said yesterday, the latest in a string of attacks targeting associates of Iraq's leading Shiite cleric.
Also, civilian deaths rose in August to their second-highest monthly level this year, but American combat deaths in Iraq have dropped by half in the three months since the buildup of 28,000 additional U.S. troops reached full strength.
U.S. officials had predicted that the increase would lead to higher American casualties as the troops "took the fight to the enemy." But that hasn't happened, although U.S. forces have launched major offensives with thousands of troops north and south of Baghdad.
American combat casualties have dropped to their lowest levels this year, even as violence involving Iraqis remains high.
The shooting of al-Sistani's aide Friday night was a sign of continuing tensions after clashes between Shiite militias last week. Police said Muslim Battat, an imam and preacher, was killed after evening prayers at a central Basra mosque.
The Supreme Islamic Iraqi Council, the country's biggest Shiite political group, claims allegiance to al-Sistani. That puts its followers at odds with those loyal to radical Shiite cleric Muqtada al-Sadr.
Last week, clashes erupted between the militias of the two groups. More than 50 people were killed in the fighting in the southern city of Karbala, which raised fears of all-out warfare between the Shiite militias.
It was the fourth time since June that someone associated with al-Sistani has been killed. In June, one of his representatives was found shot to death in Najaf. Al-Sistani's top adviser on legal affairs was stabbed to death in July. In August, another aide was shot to death in Najaf.
A guard at the al-Sistani compound was arrested and accused of stabbing the legal adviser during a robbery.
Whatever the motive for that killing or the others, the repeated targeting of al-Sistani associates underscores the ominous situation in the south, which has experienced rising violence as Britain cuts its troop strength there.
Unlike al-Sadr, al-Sistani rarely involves himself publicly in politics and lends no support to any of Iraq's political factions. But he is regarded by many of al-Sadr's militant loyalists as a barrier to their aspirations for power and influence in the Shiite south.
Al-Sadr has denied that his militia was involved in the Karbala bloodshed and has ordered it to halt activities for six months while an investigation is conducted to root out rogue elements. The U.S. military called the move "encouraging" yesterday and said that if the order held, it could allow the military to make headway in the war by focusing more on fighting Sunni Muslim insurgents.
It was not immediately clear what impact al-Sadr's announcement was having.
Early yesterday, residents said, U.S. military vehicles raided a section of Sadr City, al-Sadr's northeast Baghdad stronghold, and detained eight men.
The U.S. military announced that it had detained eight men during raids targeting Shiite militiamen. It did not say where the raids took place, but its description of the operation was similar to that described by the Sadr City residents.
According to residents, soldiers passed out leaflets accusing militias of being agents of Iran and working to increase Iranian influence in Iraq. The United States has long accused Shiite-dominated Iran of providing weapons and training to Shiite fighters in Iraq.
Figures compiled by the Associated Press from police reports nationwide show that at least 1,809 civilians were killed across the country last month, compared with 1,760 in July. That brings to 27,564 the number of Iraqi civilians killed since AP began collecting data on April 28, 2005.
According to that count, civilian deaths reached a high point during the wave of sectarian bombings, kidnappings and killings at the end of last year - 2,172 in December and 1,967 in November.
Tina Susman writes for the Los Angeles Times. The Associated Press and McClatchy-Tribune contributed to this article.