An image taken from video shows armed men in the southern oil port of Basra.
Iraqi Prime Minister Nouri al-Maliki on Wednesday issued a 72-hour deadline for militants in Basra to lay down their weapons after a second day of fighting left dozens dead and more than 200 wounded.
Al-Maliki arrived in Basra to supervise a crackdown against the violence spawned by militia factions who are vying for control of the center of Iraq's oil industry, which is located near the Iranian border.
Sadiq al-Rikabi, a chief adviser to al-Maliki, said gunmen who fail to turn over their weapons to police stations in Basra by Friday will be targeted for arrest. He added that they also must sign a pledge renouncing violence.
"Any gunman who does not do that within these three days will be an outlaw," he said.
More than 50 people have been killed and 300 wounded in Basra and Baghdad after clashes between Iraqi security forces and fighters loyal to Shiite cleric Muqtada al-Sadr spread to Baghdad's principle Shiite district of Sadr City.
During the past two days, the fighting between government forces and al-Sadr's followers has spread to other towns in southern Iraq where al-Sadr is influential. Officials fear a cease-fire that al-Sadr imposed on his Mahdi Army militia last August may completely unravel.
Suspected Shiite extremists fired rockets or mortars against the U.S.-protected Green Zone in central Baghdad for the third day this week. Three Americans were seriously injured in the attacks Wednesday, U.S. Embassy spokeswoman Mirembe Nantongo said.
At least four Iraqis also were killed after at least two mortar or rocket rounds fell short in Shiite areas of Baghdad.
The resumption of intense fighting by the Mahdi Army militia is a threat to U.S. soldiers and the security gains that Washington, D.C., has hailed as a sign that Iraq is on the road to recovery.
From NPR and wire reports