The wails echoed off the tile surfaces of the emergency room at Yarmouk Hospital. Amid the blood and stretchers, Majeed Aboud turned his tear-stained face to the body of his 5-year-old son, Mohammad, one of at least 34 children killed when a car bomb exploded as they gathered around U.S. soldiers handing out candy and cakes in a southern Baghdad neighborhood.

The child's thin body was covered by a sheet. The sheet was covered with blood.

"My boy was playing around with other kids when the first car bomb exploded," Aboud said when he recovered the ability to speak. "I brought him here, but they could do nothing for him."

"Why? Why?" a mother asked as a doctor bent over the bloodied chest of Russul Abbas, whose entire front was perforated by bits of metal smaller than dimes. "Why does this have to happen to my 8-year-old kid?"

Even for September, a month that saw more than 40 car bombs detonated in Iraq, Thursday's violence was extraordinary for its callousness and the number of innocents killed. At least 41 people died, including an American soldier. U.S. forces bombed Fallujah and mounted a surprise offensive overnight to retake Samarra, another restive Sunni Triangle city. Arabic-language news channels reported that kidnappers claimed to have taken 10 new captives.

But it was the young victims -- by far the most children killed in one incident since the U.S.-led invasion 17 months ago -- who galvanized the capital.

Most had gathered around American soldiers after a ribbon-cutting ceremony at a new sewage treatment plant, an event designed to show that not all the news in Iraq is bad. The soldiers were passing out sweets to the children.

An officer of the Iraqi National Guard, which was responsible for securing the area, said a Nissan pickup truck parked near the plant apparently was detonated by remote control. Half an hour later, as parents carried away the wounded and ambulances pushed through the throngs who rushed to help, a gray Daewoo sedan nudged into the crowd and exploded.

Ten Americans were reported wounded at the scene, two of them seriously. Afterward, as volunteers searched the ground for bits of flesh to fold into plastic bags, outrage so often directed at U.S. forces in the wake of such attacks was thrown wholly toward those most directly responsible.

"What kind of resistance is this?" Majeed Hameed, who lost a child, shouted again and again at the hospital. "Why do they attack children?"

Late in the day, a Web site known as a clearinghouse for Islamic militants posted an assertion of responsibility for three "heroic operations" by Monotheism and Jihad, the organization headed by Abu Musab Zarqawi, a Jordanian who U.S. officials say has links to al Qaeda.

The claim jibed with the number of sites car-bombed Thursday.

The first blast occurred about 8:30 a.m. outside the municipal building in Abu Ghraib, the Baghdad suburb where a sprawling prison is located. As three U.S. military combat vehicles entered the municipal compound, a truck laden with gasoline and explosives exploded, killing a U.S. soldier and two Iraqi police officers and damaging a heavily armored Bradley Fighting Vehicle, according to the U.S. military. Three Americans and 10 Iraqis were wounded.

"I could see bodies flying in the air," said Salman Fadhel, a municipal worker. "When I heard the blast, I thought it was doomsday."

Another car bomb exploded in Tall Afar, the city in the far north where insurgents and U.S. forces clashed for several days this month. The suicide bomber targeted a passing police patrol, killing four Iraqis and wounding 16, according to the manager of the local hospital.

"We are obviously seeing a major onslaught by the terrorists on Baghdad and some other Iraqi cities," Barham Salih, the deputy prime minister of Iraq's interim government, said at a news conference.

Salih and Prime Minister Ayad Allawi, who spoke in London, emphasized that the attacks would not dissuade Iraqi authorities from going forward with national elections promised for January.

But Salih also indicated that a military effort to reclaim areas now held by insurgents -- most notably the western city of Fallujah -- would go forward in October, at least a month earlier than senior U.S. officers in Iraq have indicated in private conversations.

"Our hope is that we will regain control of these situations as soon as possible," Salih said. "The month of October begins tomorrow. And we hope to regain control of these areas before the month of November."

That schedule appears ambitious, given what U.S. and Iraqi officials have described as deficits in both the numbers and the training of Iraqi soldiers and other security personnel. The lack of training was vividly illustrated by Iraqi National Guardsmen at the Baghdad ceremony. They overlooked the truck bomb even though the vehicle was parked inside an area that supposedly had been secured, an oversight acknowledged by Lt. Ahmad Saad, a guardsman.

Readiness of the Iraqi forces is crucial to restoring at least nominal government control in disputed areas. While U.S. troops would be expected to carry out assaults on insurgent strongholds, the task of enforcing civil order after any battle would fall to Iraqis, senior U.S. and Iraqi officials have said.

"We still need time to fully equip and train our security forces," Salih acknowledged.

Within hours, the U.S. 4th Infantry Division appeared to make good on Salih's vow in Samarra, a city about 65 miles north of Baghdad that has been largely under insurgent control in recent months. A military statement issued in the early hours of Friday said troops from two Iraqi battalions -- one regular army, the other national guard -- and the 1st Infantry Division "secured key government buildings and locations."

Several battalions from the 4th Infantry Division entered the city at 6 p.m. Thursday, and encountered what a spokesman described as intermittent but never-heavy resistance through the night. The first clashes were from the bridge into the city over the Tigris, from which 4th Infantry Division forces engaged and destroyed three speed boats and killed four insurgents firing from aboard hem. Two other boats were later destroyed as well.

"There was sporadic gunfire and rocket-propelled grenade fire at elements throughout the city," said Staff Sgt. Robert Powell, a 4th Infrantry Division spokesman. "It was really scattered throughout the city."

Powell said the military estimated 71 enemy dead and one wounded, with no reported casualties among the 4th Infantry Division or the Iraqi forces.

Meanwhile on Thursday, U.S. Marines who have not entered Fallujah since April continued to call in airstrikes on buildings in Fallujah where informants say Zarqawi's forces are gathering. At 5 a.m., U.S. bombs leveled two houses in the central neighborhood of Officers. Hospital officials said the dead included a woman and a child, as well as Iraqi fighters.

"I knew they would attack my house because my neighbor hosts suspect guests, and cars without license plates park in front of his house," said Ali Eid Dulaimi, whose house was destroyed. He blamed the insurgents.

"They caused the killing of my mother and nephew," Dulaimi said. "I will not live in Fallujah anymore."

But proximity to Americans also carries profound risks, as Iraqis have learned. In Amel, the Baghdad neighborhood whose name means "worker," Amer Abed forbade his children to attend the plant-opening ceremony being held 30 yards from their home.

"I told them not to go, because I felt something bad would happen," he said. "There were too many Americans gathering."

The first explosion spewed shrapnel into Abed's yard, and it penetrated the leg of his daughter, Farah, who was playing outside. After he carried his crying child inside, the second explosion broke the windows of his house.

"I am one of those who hate the Americans and reject the idea that they are here, but attacking them while they were among innocent people is considered a big crime," said Abed, 46. "I understand that the resistance wants to get rid of the Americans, but this is not the right way to do it."

Two wounded boys are treated at Yarmouk Hospital in the Iraqi capital after explosions that killed at least 34 children and seven adults. A police officer warns people away from the site of a bomb attack in a Baghdad neighborhood where a new sewage treatment plant was being opened.