BAGHDAD &

Rescuers dug through the muddy wreckage of collapsed clay houses in northwest Iraq today, uncovering at least 200 victims of suicide truck bombings that the U.S. military blamed on al-Qaida.

The victims of the war's second-deadliest attack were members of a small Kurdish sect, the Yazidis, who have been the target of Muslim extremists who consider them infidels.

Police said separately that five people were killed in an ambush today on a minibus carrying civilians near Khalis, about 50 miles north of Baghdad, where suspected al-Qaida militants had set up a fake checkpoint. A 5-year-old was among the dead.

In the main northern city of Mosul, a bomb in a parked car killed a civilian and wounded ten others, police and army officers said. A police patrol appeared to have been the target.

South of Baghdad, meanwhile, a suicide car bomber killed two people and wounded seven, Iraqi police said.

Tuesday's four suicide truck bombers struck nearly simultaneously, killing more people than any other concerted attack since Nov. 23, when 215 people were killed by mortar fire and five car bombs in Baghdad's Shiite Muslim enclave of Sadr City.

Some 300 people were wounded in the attacks on the Yazidis, an ancient religious community, said Dakhil Qassim, the mayor of the nearby town of Sinjar.

The carnage dealt a serious blow to U.S. efforts to pacify the country with just weeks before top U.S. commander Gen. David Petraeus and U.S. Ambassador Ryan Crocker are to deliver a pivotal report to Congress amid a fierce debate over whether to begin withdrawing U.S. troops from Iraq.

U.S. officials believe extremists are attempting to regroup across northern Iraq after being driven from strongholds in and around Baghdad, and commanders have warned they expected Sunni insurgents to step up attacks in a bid to upstage the report.

Army Maj. Gen. Benjamin Mixon, the commander of U.S. forces in northern Iraq, said last month that he proposed reducing American troop levels in Ninevah and predicted the province would shift to Iraqi government control as early as this month. It was unclear whether that projection would hold after Tuesday's staggering death tolls.

Qassim said the four trucks approached the town of Qahataniya, 75 miles west of Mosul, Iraq's third-largest city, from dirt roads and all exploded within minutes of each other. He said the casualty toll was expected to rise.

"We are still digging with our hands and shovels because we can't use cranes because many of the houses were built of clay," Qassim said. "We are expecting to reach the final death toll tomorrow or day after tomorrow as we are getting only pieces of bodies."

"The car bombs that were used all had the consistent profile of al-Qaida in Iraq violence," U.S. military spokesman Brig. Gen. Kevin Bergner told reporters in Baghdad's heavily fortified Green Zone.

The U.S. military issued a statement putting the death toll in the Qahataniya bombings at 60. The Iraqi estimate of more than 200 deaths was based on body counts from local hospitals and morgues to which U.S. officials had no access.

Iraqi Prime Minister Nouri al-Maliki issued a statement blaming the bombings on "terrorism powers who seek to fuel sectarian strife and damage our people's national unity."

The Yazidis are a primarily Kurdish religious sect with ancient roots that worships an angel figure considered to be the devil by some Muslims and Christians. Yazidis, who don't believe in hell or evil, deny that.

The Islamic State in Iraq, an al-Qaida front group, distributed leaflets a week ago warning residents near the scene of Tuesday's bombings that an attack was imminent because Yazidis are "anti-Islamic."

The sect has been under fire since some members stoned a Yazidi teenager to death in April. She had converted to Islam and fled her family with a Muslim boyfriend, and police said 18-year-old Duaa Khalil Aswad was killed by relatives who disapproved of the match.

A grainy video showing gruesome scenes of the woman's killing was later posted on Iraqi Web sites. Its authenticity could not be independently verified, but recent attacks on Yazidis have been blamed on al-Qaida-linked Sunni insurgents seeking revenge.

A curfew was in place today across towns west of Mosul, and U.S. and Iraqi forces were conducting house-to-house searches in response to the bombings, according to Iraqi police and Army officers who spoke on condition of anonymity out of security concerns. Twenty suspects were arrested, they said.

Meanwhile, U.S. troops killed 11 suspected terrorists and detained four others in operations against al-Qaida in central and northern Iraq, the military said in a statement.

Ten thousand U.S. troops and 6,000 Iraqi soldiers are involved in air and ground assaults across Diyala and Salahuddin provinces, both north of Baghdad, in a nationwide offensive against Sunni insurgents with links to al-Qaida and Shiite militiamen.

More than 300 artillery rounds, rockets and bombs were dropped in the Diyala River valley late Monday and early Tuesday, and three suspected al-Qaida gunmen were killed and eight were taken prisoner, the military said. U.S. troops also discovered several roadside bombs rigged to explode.