The attacks followed a series of clashes last week between US and Iraqi forces and factions of the Mahdi Army, the biggest Shiite militia loyal to radical cleric Muqtada al-Sadr.
Al-Sadr led two uprisings against US-led coalition forces in 2004. Last August he declared a six-month cease-fire to purge the militia of criminal and dissident elements.
US officials have cited the truce, which al-Sadr recently extended, among the reasons behind a 60 percent drop in violence since President Bush ordered 30,000 US reinforcements to Iraq early last year.
But the cease-fire has come under severe strains in recent weeks. Al-Sadr's followers have accused the Shiite-dominated government of exploiting the cease-fire to target the cleric's supporters in advance of provincial elections expected this fall.
Al-Sadr recently told his followers that although the truce remains in effect, they were free to defend themselves against attacks. Al-Sadr followers have demanded the release of supporters rounded up in recent weeks.
US officials have insisted they are not going after Sadrists who respect the cease-fire but are targeting renegade elements, known as special groups, that the Americans believe have ties to Iran.
But the pattern of the attacks against the Green Zone could be a signal to the Americans and their Iraqi partners to ease their pressure against mainstream Sadrists or the special groups.
Elsewhere, 12 gunmen were killed Sunday in a raid against a suspected suicide bombing network east of Baqouba, the US military said.
Iraqi police reported a dozen civilians killed in an airstrike in the same area. But the military said those killed in the raid were insurgents, including six who had shaved their bodies apparently in preparation for suicide operations.
A police commander was shot to death along with his driver in Balad Ruz, 45 miles northeast of Baghdad.
A roadside bomb near the northern city of Tuz Khormato killed four Iraqi soldiers, including an officer.
The violence was reported by police officials who declined to be identified because they weren't supposed to release the information.
(China Daily via Agencies March 24, 2008)
