Troops Pushing South Through Insurgent Area

On the ground, the soldiers are moving methodically on foot, searching every house for weapons and attempting to catalogue the local population. So far they have destroyed 17 weapons caches, commanders said.

The American troops established their headquarters, known as Patrol Base Murray, inside a sprawling riverside estate with polished granite floors, orchards out front and an empty swimming pool in the back. While insurgents have sent mortar fire toward the base without causing injuries, a close call occurred at 7:45 p.m. Thursday when a rocket-propelled grenade crashed down on a dirt berm about 75 yards from the house.

At the sound of the bang, soldiers sprinted inside and slung on their helmets and flak jackets. Gunners on the roof saw a plume rising from amid the palm trees north of the estate. First Sgt. Robert Tetu jumped on the radio.

"Why aren't we shooting at that damn area if we see a smoke trail?" he barked. "This shouldn't take so long."

The guns roared. Up on the roof, Sgt. Lauren Hoeppner, 28, fired off six armor-piercing incendiary rounds into the foliage. Another gunner shot more than 60 bullets from his M240 machine gun.

"We're getting attacked!" someone shouted downstairs.

The grenade landed near a pumping station next to the outpost, where two children were playing. Within minutes, a boy, about 3 years old, was carried to the entrance of the base with a head wound caused by shrapnel. The girl, about 5, was brought in with more serious wounds to her left leg. The soldiers treated the children, who returned home late Thursday night.

"These guys have been doing that ever since we got out here," Hoeppner said of the attackers.

Elsewhere in Iraq, the deadliest strike against U.S. forces occurred Thursday in northeast Baghdad. Five soldiers, three civilians and an Iraqi interpreter were killed when a roadside bomb exploded near the soldiers' vehicle during combat operations, the U.S. military said in a statement. In northern Baghdad, a soldier was killed and three others were injured about 12:30 p.m. Thursday when their vehicle was struck by a rocket-propelled grenade. On Wednesday, four U.S. soldiers were killed when a roadside bomb hit their convoy in western Baghdad, and two Marines were killed during combat operations in Anbar province, west of the capital.

In the northern operation, called Arrowhead Ripper, in which a U.S. soldier's death Tuesday was announced earlier, the U.S. military reported that 11 people were wounded Wednesday when a U.S. plane mistakenly bombed the wrong target in the Khatoon area of Baqubah. The incident, first reported Thursday in The Washington Post, occurred when soldiers clearing a house discovered it was booby-trapped and called in an airstrike that hit the wrong house. A helicopter later destroyed the correct target with a Hellfire missile.

The Associated Press reported that the house bombed mistakenly was the headquarters of a Sunni insurgent group called the 1920 Revolution Brigades, which is cooperating with U.S. forces and helping them to identify al-Qaeda in Iraq members and facilities in Baqubah. A spokesman for the group told the AP that the bomb killed two of its members and wounded four.

In an unrelated development, 15 people were killed and 72 were injured when a suicide truck bomber crashed an oil tanker into a municipal headquarters in the small Sunni-Turkmen town of Sulaiman Bek, about 60 miles south of the northern city of Kirkuk, and detonated it, local police and hospital officials said. The explosion demolished the offices of the mayor, town council and police, according to regional police Col. Abbas Mohammed Amin. Two policemen were killed, and 20 police officers and two council members were wounded, hospital officials said.

Meanwhile, as many as nine mortar shells slammed into Baghdad's Green Zone on Thursday morning, including one that reportedly landed in the parking lot used by Prime Minister Nouri al-Maliki. There were no reports of injuries.

The heavily fortified Green Zone -- a walled compound of about five square miles on the banks of the Tigris that is headquarters for the Iraqi government and U.S. forces -- has come under increasing attack this year. A U.N. report earlier this month said that more than 86 mortar and rocket attacks had hit the Green Zone from the beginning of March through May 22 and that at least 26 people had been killed in attacks since mid-February.

Anderson reported from Baghdad. Other Washington Post staff in Iraq contributed to this report.