BAGHDAD, June 17 -- Dozens were killed in a series of explosions in Baghdad on Saturday, a major setback for the government's efforts to crack down violence in the country's capital.

Iraqi youths mourn the death of a relative outside a local hospital in Baghdad. [Xinhua/Reuters Photo]

Prime Minister Nuri al-Maliki launched a security crackdown in Baghdad since Wednesday with 50,000 Iraqi troops supported by 7,000 U.S. troops. But the rebounding violence showed the serious challenges that al-Maliki has to face.

In the latest attack, also the worst one on Saturday, a car bomb killed 12 and wounded 38 in the southwest of Baghdad, an Interior Ministry source told Xinhua.

The car bomb, targeting an Iraqi police patrol, went off in Aalam district in the area at around 8:00 p.m. (1600 GMT), the source said.

Earlier in the morning, two were killed and 14 others wounded when mortar rounds landed at a popular market in a northern Baghdad district, an Interior Ministry source said.

The source said the shells hit the Aster Badi market at the mainly Shiite Kazmiyah neighborhood, causing damage to several nearby shops and buildings.

Then at about 10:15 a.m. (0615 GMT), an explosive charge went off at a crowded market in central Baghdad, killing six and wounding 11 others, police source said.

Just an hour later, 11 people were killed and 15 wounded in a suicide car bomb attack on Iraqi security patrols in central Baghdad.

The attack occurred at about 11:15 a.m. (0715 GMT) when a suicide bomber drove his explosive-packed car into Iraqi police and army patrols at Elwiyah neighborhood, killing ten civilians and one soldier, said an Interior Ministry source, adding that eight soldiers, three policemen and four civilians were also wounded.

At around 1:00 p.m. (0900 GMT), four civilians were killed and 11 others wounded when a homemade bomb went off in a minibus in eastern Baghdad, an Interior Ministry source said.

In another development, the U.S. military said on Saturday that a U.S. soldier was killed and two others went missing on Friday when insurgents attacked them at a traffic checkpoint south of Baghdad.

The statement said coalition forces were searching for the missing soldiers in the area.

The death toll of U.S. soldiers killed in Iraq since the invasion in March 2003 had breached the psychological benchmark of 2,500, according to Pentagon figures.

The new wave of attacks came just one day after a suicide bomber blew himself up in a prominent Shiite mosque in central Baghdad, killing ten and wounding 25.