By Ernesto Londoño
Washington Post Foreign Service
Monday, April 21, 2008; A12

BAGHDAD, April 20 -- Heavy fighting broke out in Baghdad on Sunday following a particularly deadly night in the eastern part of the city. The clashes came a day after Shiite cleric Moqtada al-Sadr threatened to wage an open war against U.S.-backed Iraqi security forces.

U.S. troops killed at least 18 suspected militia members Sunday in airstrikes and other attacks, the military said.

U.S. forces have been conducting near round-the-clock aerial surveillance of the Shiite Sadr City district of the capital in an effort to prevent rocket and other attacks. Many of the rockets fired into the Green Zone and at other U.S. and Iraqi government facilities originate in Sadr City and adjacent neighborhoods.

Early Sunday, U.S. soldiers opened fire on a group of men planting a roadside bomb, the military said. The device exploded, killing three of the suspected militia members. Later, in the same neighborhood, U.S. soldiers killed nine men carrying machine guns, rifles and a rocket-propelled grenade launcher.

At least two suspected militiamen were killed in aerial strikes in Sadr City, and a third was fatally shot by U.S. troops, the military said. Three people were killed in a missile strike late Sunday, it said.

The airstrikes in Sadr City have enraged Sadr's followers, who say they are awaiting his order to officially suspend a cease-fire.

Prime Minister Nouri al-Maliki, following a meeting with U.S. Secretary of State Condoleezza Rice, issued a statement calling his government's military raids against Shiite militias in the southern city of Basra last month a "strong blow to all lawbreakers." He vowed also to take on Sunni extremists in the city of Mosul.

The Sunni insurgent group al-Qaeda in Iraq has stepped up attacks across the country in recent days, killing dozens of civilians. Mosul remains one of its strongholds.

Maliki also said the Iraqi government had made significant progress in working across sectarian lines.

Iraqi President Jalal Talabani announced that the Sunni Arab bloc that broke away from the government last year is poised to return. The bloc, the Iraqi Accordance Front, has given the government a list of nominees to head ministries it formerly ran.

Meanwhile, Iraqi officials found two mass graves containing 47 bodies in Diyala province, according to Maj. Gen. Abdel-Karim al-Rubaie, an Iraqi military spokesman.

Sadr issued a new statement Sunday night condemning Rice's visit and denouncing a reported raid on a Sadr office in Nasiriyah, a city in southern Iraq. A spokesman for Sadr said Iraqi security forces killed 15 members of the group during a raid on a cultural center.

Maj. Gen. Ghalib al-Jazaery, a police official in Nasiriyah, said tribesmen, not security forces, had raided the building. He said the tribesmen were retaliating against Shiite militia attacks.

Special correspondents Zaid Sabah and Naseer Nouri in Baghdad and Saad Sarhan in Najaf contributed to this report.

The family of Jonathon Cote, a contractor kidnapped in Iraq in November 2006, said Sunday that a body that could be his has been recovered in southern Iraq.

U.S. officials informed the family of the discovery near Basra, they said on the Web site Free Cote. The body will be flown to Dover Air Force Base in Delaware, where it will be identified and an autopsy performed, according to the Web site. Cote's family declined to comment until the body is identified.

-- Associated Press