A suspected Sunni truck bomber attacked a revered Shiite shrine in the heart of Baghdad on Tuesday, a resumption of Iraq's relentless sectarian slaughter that killed at least 78 people and wounded more than 200. The mosque's turquoise dome survived, but the blast buried some worshippers and badly burned others. Northeast of Baghdad, a force of 10,000 US soldiers firing artillery and using heavily armored Stryker and Bradley Fighting Vehicles fought their way through western Baqouba and other al-Qaida sanctuaries in Diyala province. US helicopters and jet fighters flew cover. In all 142 people were killed or found dead in sectarian violence Tuesday, a toll reflecting carnage associated with the months before the US security crackdown in the capital began Feb. 14. The Pentagon is required to issue an initial assessment of the operation next month, and Gen. David Petraeus, the top US commander in Iraq, will report in September. The Democrat-controlled Congress set those reporting deadlines to pressure the White House and American military leadership to make quick progress in curbing violence here so US troops - now 155,000 - can be pulled away from the increasingly unpopular war. American commanders have said there will positive results by September but that any return to normalcy requires years. US President George W. Bush has even spoken of the US mission in Iraq in terms of the 50-plus-year American troop presence in South Korea. Tuesday's bombing was a critical setback. Police said a truck piled high with electric fans and air conditioners delivered the huge bomb at the Khulani mosque. The powerful explosion in the busy commercial district cut deep into Iraq's Shiite community on just the second day after authorities lifted a four-day curfew in the capital. The vehicle ban was imposed to clamp off potential revenge attacks after a bombing last week brought down twin golden minarets at the important Shiite al-Askariya shrine in Samarra, north of the capital. The bombing that destroyed the golden dome there in Feb. 26 set in motion the sectarian bloodletting that has sundered the sectarian fault line in Iraq. The mosque imam, Sheik Saleh al-Haidari, said the bomb killed so many because worshippers were just leaving a prayer service. "This attack was planned and carried out by sick souls," al-Haidari told The Associated Press by telephone. He said his office and the room above collapsed, but he was not in the mosque when the bomb exploded. Karim Abdullah, the 35-year-old owner of a nearby clothing store, said he was on his way to pray at the mosque when the explosion caused his motorcycle to wobble under him. "I stopped in shock as I saw the smoke and people on the ground. I saw two or three men in flames as they were getting out of their car," he said. Associated Press reporters said gunfire rattled through the district after the truck exploded in a parking lot near the mosque. A courtyard wall collapse and building just inside the mosque compound was turned to rubble. The mosque sanctuary was slightly damaged. The Khulani mosque is named after a much-revered Shiite figure who, according to the sect's tradition, was one of four "earthly" deputies anointed by the Imam Mohammed al-Mahdi, who disappeared in the 9th century. Shiites believe the so-called "Hidden Imam" will return to Earth to restore justice to humanity. Police and officials at al-Kindi, Iman Ali, al-Sadr and Medical City hospitals said at least 78 people were killed and 218 were wounded, adding that the toll could rise as bodies were pulled from the debris. The officials spoke on condition of anonymity because the feared retribution. The US military said the bombing was a suicide attack and that its unit in the area recorded 35 killed and 65 wounded at al-Kindi hospital. The military did not check other facilities for dead or wounded. Lt. Col. Scott Bleichwehl, a military spokesman in Baghdad, said the truck was loaded with propane tanks and the suicide driver detonated his bomb when the vehicle became stuck trying to drive over a curb. It was impossible to reconcile the difference in the police and military accounts about the truck's cargo or whether it was a parked bomb or suicide driver. Six of those killed lived in a house behind the mosque, a police official said. Twenty cars were incinerated and 25 shops damaged. The US military operation in Diyala province, an al-Qaida bastion, matched in size the force American generals sent against the insurgent-held city of Fallujah 2 1/2 years ago. Additionally, Iraqi forces - about 5,000 Iraqi soldiers and 2,000 paramilitary police - joined the battle, according to Mohammed al-Askari, the defense ministry spokesman. The US commander in the region, Maj. Gen. Benjamin Mixon, said the combined US-Iraqi force of about 3,500 soldiers and police were operating in Baqouba proper, a city of about 300,000. "We began last night with large-scale air assaults moving by helicopter to surprise the enemy with a large ground assault before daylight. We've had initial good success....There's a lot of work left to be done," he told CNN. The military said at least 22 militants had been killed by daybreak. In southern Iraq, police and hospital officials said the death toll reached 30 in clashes that continued into a second day between Mahdi Army fighters and Iraqi security forces in Nasiriyah, about 200 miles southeast of Baghdad. Authorities said about 150 people were wounded. They declined to be identified because they feared retribution. Most of the casualties were police or militiamen. A delegation from radical Shiite cleric Muqtada al-Sadr's office arrived in the city to try to end the fighting, according to the city council. A curfew was imposed on Nasiriyah on Monday, and remained in effect. At sundown Tuesday, militants fired a volley of mortars into the US-guarded Green Zone. Five crashed to earth near the office of Prime Minister Nouri al-Maliki and one slammed into a structure adjacent to the American post exchange store. No casualties were immediately reported. The American Embassy confirmed that the Green Zone had been hit by mortar or rocket fire but provided no details.