The U.S.-led coalition in Iraq says there is an arrest warrant for radical Shi'ite Muslim cleric Moqtada al-Sadr.
The warrant, issued several months ago, accuses Mr. al-Sadr and at least 30 accomplices of the murder of a rival last year in ajaf.
Moqtada al-Sadr is reported holed up in the main Shi'ite mosque in the central city of Kufa, surrounded by armed supporters.
Elsewhere in Baghdad, coalition forces fired on armed Shi'ite Sadr supporters, after insurgents opened fire on a U.S. helicopter.
In Fallujah, hundreds of U.S. and Iraqi troops closed all roads leading to the town. Western journalists reported explosions and gunfire coming from the center of the city.
News of the Sadr arrest warrant comes after clashes Sunday between the cleric's armed supporters and coalition forces killed nearly 60 people. Those killed including eight U.S. troops and one Salvadoran soldier.
The Foreign Minister of Qatar, Sheikh Hamad bin Jassim al-Thani, said the latest violence in Iraq could degenerate into a civil war.
Visiting (the southern U.S. state of) North Carolina, Monday, President Bush said June 30th remains the "firm" date for the transfer of power in Iraq - despite the latest violence.
Information for this report is provided by AFP, AP and Reuters.