The U.S. military said a U.S. airstrike killed six and wounded an unknown number of people near the Sadr City area of Baghdad after a tank patrolling the area was fired upon, Alalam satellite television reported. Another three men were killed in a separate incident.

The Iraqi military operation set off clashes between security forces and militias, including followers of cleric Moqtada Sadr in Basra and other areas in southern Iraq.

Fighting between government troops and militias picked up Tuesday in Basra but was confined to several sectors of the city, reported KUNA, the Kuwaiti news agency. Fighting between Sadr's followers and troops also was reported in other southern towns.

Liwa Sumaysim, head of Sadr's political bureau, said if these reports were true, the government forces are "breaking the truce."

Maliki's office said the prime minister "has ordered a halt to all kinds of raids and arrests without warrants."

In Baghdad, a three-day curfew was mostly lifted but mortar shells and rockets struck the Green Zone government and diplomatic compound, Alalam reported.