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

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 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 the 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 U.S. soldiers also were reported killed, including five in a helicopter crash.

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

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.

Meanwhile, the U.S. military heralded success in Day Two of a nationwide offensive against Sunni insurgents with links to al-Qaida and Shiite militiamen. Ten thousand U.S. troops and 6,000 Iraqi soldiers were involved in air and ground assaults.

More than 300 artillery rounds, rockets and bombs were dropped in the Diyala River valley late Monday and early Tuesday, the U.S. military said in a statement. Three suspected al-Qaida gunmen were killed.