Iraqi security forces battled Shiite gunmen south of Baghdad on Friday, raising tensions among rival factions of the majority religious community and straining a seven-month cease-fire with the largest Shiite militia. The fighting in Kut, 100 miles southeast of Baghdad, broke out Thursday night when factions of the Mahdi Army, led by anti-American cleric Muqtada al-Sadr, attacked checkpoints throughout the city, officials said. Two policemen and two gunmen were killed, said the Iraqi Interior Ministry.

The U.S. command said that an American soldier was killed Friday and four others were wounded in a rocket or mortar attack south of the capital. The statement did not provide more details; the area has a volatile mix of Sunni and Shiite extremists. At least 3,993 members of the U.S. military have died from all causes since the beginning of the war five years ago, according to an Associated Press count.

The U.S. military released 13 detainees on Friday who were welcomed home at a ceremony in the former Sunni insurgent stronghold of Azamiyah in northern Baghdad. It was the latest in a series of releases meant as a goodwill gesture to promote reconciliation with minority Sunnis who have turned against Al-Qaida in Iraq.