BAGHDAD — Iraq's conflict entered a bloody new phase Tuesday as U.S. forces launched their largest assault ever in Diyala province and insurgents killed at least 78 people with a massive car bomb outside a Shiite mosque in Baghdad.
U.S. officials said that more than 10,000 air and ground forces had descended on Diyala province in an effort — dubbed Operation Arrowhead Ripper — to rout al-Qaida in Iraq insurgents who've killed thousands of civilians in recent months.
Details of the fighting were sketchy. Initial American military reports said 22 insurgents had been killed. No military or civilian casualty figures were available late Tuesday.
Military officials said the U.S. and Iraqi forces were met with fire from machine gun nests and snipers but that there also were instances of al-Qaida fighters attempting to avoid combat.
"The level and type of resistance varies," U.S. Army spokesman Maj. Tage Rainsford said. "In a number of cases today, al-Qaida operators attempted to move gunmen and munitions in order to circumvent the security crackdown."
Participating in the operation were the 3rd Brigade Combat Team, 1st Cavalry Division, from Fort Hood, Texas, the 4th Brigade Combat Team, 2nd Infantry Division, from Fort Lewis, Wash., and the 25th Combat Aviation Brigade, from Schofield Barracks, Hawaii, Rainsford said.
It was unclear how many al-Qaida fighters were operating in the area, where the terrorist organization has found a traditional ally in local Sunni Muslim militants.
With American Army helicopters overhead, ground troops moved into at least five neighborhoods in the western portion of the provincial capital, Baqouba, and imposed curfews. Those areas included al-Mafraq, al-Katoun, al-Mualimeen, New Baqouba and Hay al-Mustafa.
Iraqi security forces weren't involved in the initial assault, but will have a role in securing the western section of the city, U.S. military officials said.
The Hay al Mustafa neighborhood in Baqouba "was totally cleansed (of) terrorists," an Iraqi Defense Ministry statement said. Among weapons seized were swords "used to cut people's heads" off. The statement added that life in the neighborhood "was back to normal."
Diyala has become a focus of al-Qaida operations as the United States has moved more troops into Baghdad and Anbar province as part of the Bush administration's buildup of troops, designed to crush insurgent, sectarian and gangland-style killings in the capital.
U.S. troops in Iraq now number about 150,000, with more than 30,000 of those in Baghdad. Military officials promised more operations.
"The surge is just starting," American Army spokesman Lt. Col. Christopher Garver said. "We're just now kicking operations off, as we've seen. This is the surge that will go through the summer."
As ground and air forces pushed into Baqouba, a truck bomb in Baghdad's industrial al-Sinak neighborhood killed at least 78 civilians and wounded more than 200 near the Shiite Khillani mosque. The street, crammed with pedestrians and car-parts stores, is near the Sunni mosque al-Gailani, which was bombed May 28.
Last week a bomb destroyed the twin minarets at the Askariya shrine, a Shiite holy site in Samarra, 65 miles north of Baghdad. A bomb destroyed the shrine's golden dome last year, and fueled a massive increase in sectarian killings.
Shiite cleric Muqtada al-Sadr, the head of the Mahdi Army militia, has called for Shiites to gather July 7 at what remains of the Askariya shrine.
Mohammed al-Mamori, 30, who sells automotive fluids across the street from the Khillani mosque, said the explosion burned as many as 50 parked cars nearby, leaving many with charred bodies inside. Iraqi army troops at a nearby checkpoint fired into the air to disperse the stunned crowd, he said.
"It's the biggest failure of the security plan," he said. "The government is doing nothing for the Iraqis. It's as if they don't care about us at all."
Prime Minister Nouri al-Maliki said the bombing was intended "to provoke sectarian sedition." He vowed to "tighten the grip" around terrorist groups, and "strike hard and defeat them through holding to the national unity."
A spokesman for Grand Ayatollah Ali al-Sistani, a leading Shiite figure who lives in the southern city of Najaf, called Tuesday for national unity and an end to bombing all mosques.
Elsewhere Tuesday, a roadside bomb in Baghdad's downtown Yarmouk neighborhood killed three civilians.
A roadside bomb also killed an Iraqi soldier in the city's Dora area. Mortar rounds — a growing threat in Baghdad, including the fortified Green Zone — killed two civilians and injured 19 in the Zafaraniya neighborhood. Despite the security crackdown, dead bodies continue to be dumped around the capital. Police reported finding 21 corpses throughout the city Tuesday.
Separately, the U.S. military announced the death of an American soldier in Baghdad. The soldier, whose name wasn't released, was killed by small-arms fire during combat Monday in an eastern section of the capital, a military statement said. No other soldiers were wounded in the attack, it said.
(Drummond reports for The Charlotte Observer. Hammoudi is a McClatchy Newspapers special correspondent.)