Separate bomb blasts across Iraq Thursday killed more than 40 people, most of them children, in a dramatic escalation of the country's violent insurgency that also injured hundreds of Iraqis and numerous American troops.

The most lethal attack appeared to be directed at a government-sponsored ceremony marking the reopening of a water treatment plant in the Baghdad neighborhood of al Amel in the city's Bayaa district. But among the victims were at least 34 children, who had gathered excitedly in anticipation of candy and cake being handed out by U.S. troops, according to people on the scene.

There were at least three car bombs involved in the Bayaa attack, the U.S. military said, with many killed when the second attacker steered into a crowd that had gathered around an ambulance carrying away the wounded from the first explosion minutes earlier.

Separately, a car bomb killed one U.S. soldier and two Iraqi police at a checkpoint near Abu Ghraib on Thursday morning. Three American soldiers and 10 police were wounded in the Abu Ghraib attack, which also damaged a Bradley Fighting Vehicle, according to a statement by the U.S. military.

The Reuters news agency quoted a doctor at Abu Ghraib hospital saying that a total of around 60 people were wounded.

In the northern city of Tal Afar, meanwhile, police and hospital officials said an explosion killed four people and wounded 16, news agencies reported. There were conflicting accounts of what caused the blast. Military spokeswoman Capt. Angela Bowman said it was a car bomb, but police in nearby Mosul said it was a device planted in the road.

The blasts Thursday were the latest in a flurry of attacks primarily against U.S.-led forces and Iraqi security personnel. In September alone, according to a U.S. security official, more than 40 car bombs have been detonated by insurgents, many of them aimed at Iraqis being trained to supplement and ultimately replace foreign troops.

Details of the checkpoint attack were not immediately available, but a spokesman for the 1st Cavalry Division, the Army unit that has responsibility for Baghdad, issued a statement condemning the ambush.

"This despicable act killed not only a Multi National Force Soldier, but Iraqis who were merely going about their business of defending this country," said Lt. Col. James Hutton, a 1st Cavalry Division spokesman. "The terrorists offer nothing but destruction."

The western reaches of the capital, including the suburb of Abu Ghraib that includes a sprawling prison complex of the same name, long have been a center of resistance to the U.S.-led foreign presence.

The area includes several neighborhoods built to house employees of Saddam Hussein's security apparatus and others whose livelihood and identity were wrapped up in the government toppled by the invasion of Iraq.

The main highway through the area also leads to Fallujah, a city of 300,000 that has been under the control of insurgents and foreign fighters since last April. U.S. Marines no longer venture into the city, but call in airstrikes on an almost daily basis, usually on houses where informants have indicated that followers of Abu Musab Zarqawi are gathering.

At three minutes before 5 a.m. Thursday, another such strike devastated what a Marine statement called "a known terrorist safe house." The military noted that "secondary explosions" -- blasts following the airstrike -- indicated that the home had contained numerous munitions.

Agence France-Presse reported that three people were killed and six wounded, quoting Hakim Badani, a doctor at Fallujah's main hospital. It was not clear whom the casualties included.

"Multi-National forces take great care to minimize collateral damage and civilian casualties," the military statement said. "Terrorists' placement of weapons caches in homes, schools, hospitals and mosques continue to put innocent civilians at risk."

Meanwhile, al Jazeera television reported that an Iraqi militant group said it had kidnapped 10 people, including two Indonesian women who work for an electronics firm.

According to Reuters, the Arab news network aired a videotape from the "Islamic Army in Iraq, the western leadership" showing three men held captive.

It said the other hostages were six Iraqis and two Lebanese nationals, but that the group made no demands.

The tape showed two of the hostages kneeling under a black banner carrying the group's name, with masked men holding machine guns above their heads.

It was not clear if the group was a division of the Islamic Army in Iraq that is holding two French journalists hostage.

Militants have seized scores of foreign hostages in Iraq since April. Most of them have been released, but around 30 have been killed.

Barbash reported from Washington.