The main Friday prayers in the Shi'ite holy city of Najaf were canceled after scuffles broke out between supporters and opponents of radical cleric Moqtada al-Sadr.
Members of the Shi'ite political party Supreme Council for the Islamic Revolution of Iraq carried banners to the Imam Ali mosque in Najaf, voicing support for a peace plan recently threatened by two days of violence.
Shi'ite supporters of Mister al-Sadr blocked their way, and fights broke out inside the mosque. Gunfire outside sent civilians running for cover.
Friday's incident followed gunbattles between Mr. al-Sadr's militia and Iraqi police at a police station. Hospital officials say six Iraqis were killed and 29 wounded.
It was the first fighting in Najaf since a truce brokered by Shiite clerics and politicians ended eight weeks of clashes between the al-Mehdi militia and U.S. troops.
In the Iraqi capital, Baghdad, a car bomb exploded on a highway as a U.S. patrol passed nearby. Two U.S. humvees were slightly damaged.
In Seoul, South Korea's government says it will send 3600 troops to a Kurdish area of northern Iraq in August, despite public opposition. South Korea already has 600 medics and engineers in the southern city of Nasiriyah.
Seoul had planned to send troops to the northern city of Kirkuk in April, but that deployment was canceled, amid fears the troops would become involved in combat operations, violating a parliamentary mandate for peacekeeping duties only.