Baghdad ? A triple car bombing struck a busy shopping district Saturday, killing at least 51 people and wounding more than 90 in an attack timed to inflict as many casualties as possible, according to Iraqi officials.

Three parked cars exploded just before dinner time as shoppers were purchasing meat, fruit and vegetables in the bustling majority Shiite neighborhood of Sadriyah. Columns of black smoke hovered above buildings.

The bombing occurred a day after U.S. and Iraqi forces raided the nearby Sunni neighborhood of Fadhil, capturing 28 suspected Sunni Arab insurgents. It was the deadliest attack since a barrage of car bombs, mortars and missiles bombarded the Shiites slums of Sadr City on Nov. 23, killing more than 200 people.

Meanwhile, U.S. and Iraqi forces on Saturday launched an offensive in Baqouba, the provincial capital of Diyala province, about 35 miles northeast of Baghdad. The operation resulted in the arrest of 44 insurgents and the release of a 16-year-old kidnapping victim who was held for ransom for 25 days.

As the fierce clashes occurred, gunmen opened fire on a man and his son in Aswad district, west of Khalis, 10 miles northwest of Baqouba, killing them both, Lt. Ali Khayyam said.

The offensive also led to the seizure of several car bombs that were ready to detonate as well as weapons and posters that encouraged sectarian violence, Iraqi army officials said. Saturday’s operation came two days after the U.S. military said in a statement that Baqouba was fully operational.

Elsewhere, a roadside bomb killed a driver in Musayab, while armed men attacked a criminal intelligence commissioner’s house in the pre-dawn hours of Saturday in the town Askandarya. The assailants injured the commissioner and shot a missile at the house, but he started shooting back, killing two of the assailants. The gunbattle continued until Iraqi forces arrived.

In al-Wahada, 22 miles south of Baghdad, a truck rammed into a bus stop, killing about 20 people, wounding 15 and crushing several cars, police said.