A triple car bombing struck a food market in a predominantly Shiite area in central Baghdad, killing at least 51 people a day after a U.S.-Iraqi raid against Sunni insurgents in a nearby neighborhood.

Three parked cars blew up nearly simultaneously Saturday as shoppers were buying fruit, vegetables, meat and other items in the busy al-Sadriyah district.

The blasts sent clouds of black smoke over concrete high-rises in the area, which has narrow alleys that made it difficult for ambulances and fire trucks to navigate. At least 51 people were killed and 90 wounded, said police Lt. Mohammed Khayoun and hospital officials.

A cheese vendor who was wounded said the market was full of people shopping on their way home from work.

"We heard a big explosion from the western side of the area and the second from the eastern side. After one minute the third explosion took place near us," Ahmed Salman said from a hospital bed.

It was one of the worst incidents since a bombing and mortar attack killed 215 people and wounded more than 200 in the Shiite district of Sadr City in Baghdad on Nov. 23 amid escalating sectarian conflict.

Nobody claimed responsibility for the attack, but it followed a Friday raid by Iraqi forces backed by U.S. helicopters targeting Sunni insurgents in al-Fadhil, less than a (kilometer) half mile away.

The Sunni Association of Muslim Scholars in Iraq condemned the al-Fadhil raid in a statement Saturday, alleging six people were killed and 13 detained.

Iraqi police said Friday that one Iraqi soldier and two civilians were killed in the fighting, and the U.S. military said 28 people were detained.

Separately, U.S. and Iraqi forces began an offensive Saturday in Baqouba, capital of Diyala province about 35 miles northeast of Baghdad, where fighting has raged for a week between Sunni insurgents and police, the U.S. command said.

At least 36 suspected militants were detained during one pre-dawn raid in Baqouba, police said. Later in the day, state-run Iraqiya television said one al-Qaida in Iraq insurgent was killed and 43 detained, including two foreigners.

Ahmed Fuad, a senior morgue official in Baqouba, said the morgue had received 102 bodies since Nov. 22, only 20 of which had been retrieved by their families.

"We do believe that there are many bodies in some areas of Diyala province, but neither police nor ambulance could fetch them," he said.

Clashes broke out Saturday between insurgents and U.S. troops in the predominantly Sunni city of Duluiyah 45 miles north of Baghdad, police Capt. Qassim Mohammed said.

Elsewhere, a truck driving at high speed slammed into a bus stop in al-Wahada, 22 miles (35 kilometers) south of Baghdad, killing about 20 people, wounding 15 and crushing several cars, police said.

Police Lt. Muhammed Al-Shemari said the crash did not appear to be accidental because the truck, an empty fuel tanker, had no obvious mechanical problems.

The driver fled the overturned truck but was caught by witnesses and turned over to police, al-Shemari said, adding that other witnesses found a body in the vehicle's cabin.

Another police officer, who spoke on condition of anonymity because he was not authorized to discuss the probe, said the driver blamed brake failure.

A U.S. Army soldier was reported killed in fighting in the volatile Anbar province on Friday, the military said, raising to at least 2,887 the number of American military personnel who have died since the Iraq war started in March 2003.

Eight other people were killed in attacks nationwide, including a driver and his assistant who were shot to death as they were delivering soft drinks to stores in Baghdad's volatile Sunni neighborhood of Dora.

Iraqi police also found at least 46 bodies of apparent victims of sectarian death squads in Baghdad and three other towns. Forty-two were handcuffed, blindfolded and marked with signs of torture.

Meanwhile, the last of Italy's troops in Iraq returned to Rome on Saturday, a few weeks earlier than the date promised by Italian Premier Romano Prodi. Italy at one point was Washington's second largest coalition partner in Iraq, after Britain, during reconstruction efforts after Saddam Hussein was ousted nearly four years ago.