Rescuers dug through the muddy wreckage of collapsed clay houses in northwest Iraq on Wednesday, uncovering victims of four suicide bombings that Iraqi officials said killed at least 200 people in one of the worst attacks of the war.

A destroyed vehicle lies at the scene of a suicide bomb attack in Hilla, about 100 km (60 miles) south of Baghdad, August 15, 2007.

The victims were members of a small Kurdish sect - the Yazidis - sometimes attacked by Muslim extremists who consider them infidels.

Four suicide truck bombers struck nearly simultaneously on Tuesday, 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.

It was most vicious attack yet against the Yazidis, an ancient religious community in the region. Some 300 people were wounded in the blasts, said Dakhil Qassim, the mayor of the nearby town of Sinjar.

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 tolls were 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 bombings came as extremists staged other bold attacks on Tuesday: leveling a key bridge outside Baghdad and abducting five officials from an Oil Ministry compound in the capital in a raid using gunmen dressed as security officers. Nine US soldiers also were reported killed, including five in a helicopter crash.

An Iraqi policeman inspects the wreckage of a car used in a suicide bombing on a road in southern Kirkuk, 290 kilometers (180 miles) north of Baghdad, Iraq on Tuesday.

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

US 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.

The Yazidis comprise 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 websites. 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 Wednesday across towns west of Mosul, and US 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, the US military heralded success in Day Two of a nationwide offensive against Sunni insurgents with links to al-Qaida and Shiite militiamen. Ten thousand US troops and 6,000 Iraqi soldiers were involved in air and ground assaults across Diyala and Salahuddin provinces, both north of Baghdad.

More than 300 artillery rounds, rockets and bombs were dropped in the Diyala River valley late Monday and early Tuesday, the US military said in a statement. Three suspected al-Qaida gunmen were killed and eight were taken prisoner, the military said. American troops also discovered several roadside bombs rigged to explode, as well as a booby-trapped house, it said.

In the Iraqi capital, US special forces and Iraqi soldiers detained three suspected al-Qaida in Iraq leaders and four Shiite militia suspects in separate raids Tuesday, the military said. Another Shiite extremist accused of attacking US forces was captured the same day in Najaf, a Shiite holy city 100 miles south of Baghdad, it said in a statement.

Thousands of followers of radical Shiite cleric Muqtada al-Sadr took to the streets in Najaf in a peaceful protest against the detention. Demonstrators shouted anti-American slogans and called for an end to what they called random raids and rights violations targeting the movement.

The US military issued another statement Wednesday putting the death toll in the Yazidi bombings at 60. But the Iraqi estimate was based on body counts from local hospitals and morgues to which US officials had no access so the total was believed to be higher.

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

"These crimes will not prevent us from standing up to challenges and moving ahead with the political process to impose law and bring criminals and outlaws to justice," the statement said.

At least one of the trucks in Tuesday's bombings was an explosives-laden fuel tanker, police said. Shops were set ablaze and apartment buildings were reported crumbled by the powerful explosions.

"My friend and I were thrown high in the air. I still don't know what happened to him," said Khadir Shamu, a 30-year-old Yazidi who was injured in Tal Azir, the scene of two blasts.

Witnesses said US helicopters swooped in to evacuate wounded to hospitals in Dahuk, a Kurdish city near the Turkish border about 60 miles north of Qahataniya. Civilian cars and ambulances also rushed injured to hospitals in Dahuk, police said.

"I gave blood. I saw many maimed people with no legs or hands," said Ghassan Salim, a 40-year-old Yazidi teacher who went to a hospital to donate blood. "Many of the wounded were left in the hospital garage or in the streets because the hospital is small."

In other violence Wednesday, a suicide car bomber killed two people and wounded seven south of Baghdad, according to Iraqi police. And a parked car bomb targeted a police patrol in southern Mosul, killing a civilian and injuring ten others, police and army officers said.

(China Daily August 16, 2007)