Baghdad ? A truck bomber attacked a revered Shiite shrine in the heart of Baghdad on Tuesday, killing at least 78 people and wounding more than 200 in a resumption of Iraq’s relentless sectarian slaughter. The mosque’s turquoise dome survived, but the blast buried some worshippers and badly burned others.

Northeast of the capital, a force of 10,000 U.S. 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. U.S. 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 U.S. 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 U.S. commander in Iraq, will report in September. The Democratic-controlled Congress set those reporting deadlines to pressure the White House and American military leadership to make quick progress in curbing violence here so U.S. troops – now 155,000 – can be pulled away from the increasingly unpopular war.

American commanders have said there will be positive results by September but that any return to normalcy requires years. President Bush has even spoken of the U.S. mission in Iraq in terms of the 50-plus-year American troop presence in South Korea.

Tuesday’s bombing was a setback. It was the deadliest single attack in Iraq since April 18, when at least 127 civilians were killed when a bomb detonated in a parked car at a mostly Shiite market in central Baghdad.

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 had been imposed to prevent 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. A bombing that destroyed the golden dome there on Feb. 26, 2006 set in motion the bloodletting that has sundered the sectarian fault line in Iraq.

Tuesday’s bombing was presumed to have been carried out by a Sunni attacker because the target was a Shiite mosque. The Khulani mosque’s imam, Sheik Saleh al-Haidari, said bombing was particularly deadly 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 that he was not in the mosque at the time of the attack.

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.