The deadliest attack in the day took place when a suicide bomber blew up an explosive-laden truck near an office of Patriotic Union of Kurdistan, Iraqi President Jalal Talabani's party, in the Tabaqchali neighborhood in northern city of Kirkuk, local police said.

A car bomb parking in the same neighborhood detonated coordinately, he added.

Up to 80 people were killed and more than 170 others wounded by the twin attacks, including many women and children, the source said.

The powerful blasts almost damaged all buildings of the neighborhood and caused the collapse of dozens of nearby houses and shops, he said, adding that some 50 vehicles caught fire by the blasts and several people were charred inside their cars.

Kirkuk, 250 km north of Baghdad, has witnessed increasing tension as Arab and Turkmen population in the city are fighting Kurdish efforts to join the city to their autonomous region just to the north.

In Baghdad, at least 16 people were killed and 35 others wounded by car bombs, roadside bombs and mortar barrage on Monday, as the Iraqi police collected 25 corpses in the capital during the day, an Interior Ministry source said.

A roadside bomb detonated near an Iraqi army patrol in the Bob al-Sham area in northern Baghdad in the morning, killing five soldiers and wounding another, the source said.

In southern Baghdad, mortar rounds landed on the Abu Dsheer neighborhood, killing two people and wounding six others, he added.

A suicide car bomber rammed his explosive-laden car into a checkpoint manned by police commando members in the Harthiyah neighborhood in the afternoon, killing a commando member and a civilian and wounding 12 people, including four commando members.

Another car bomb killed two women and wounded five others when a car of a man who was freed by his kidnappers detonated in Baghdad's eastern neighborhood of Zaiyouna.

The victims were family members of the car owner who had returned home after being freed by his kidnappers. The police said that the kidnappers apparently booby-trapped the man's car before they released him in order to detonate it when he went back home.

In central Baghdad, a car bomb went off at a residential area in Karradah district, killing a civilian and wounding three others. The blast also damaged two nearby shops, the police said.

Mortar rounds struck a northern Baghdad neighborhood in the evening, killing four people and wounding eight others.

"Several mortar rounds landed on the Husseiniyah neighborhood in the evening, killing four people and wounding eight others," the source told Xinhua on condition of anonymity.

In addition, the Iraqi police patrols picked up 25 unidentified bodies from Baghdad's streets during the past 24 hours, the source added.

The bullet-riddled bodies were bound, blindfolded, showing signs of torture, he said.

Meanwhile, the U.S. military said that its troops launched a massive assault against insurgents' strongholds in the vast rural area south of Baghdad on Monday.

The offensive, dubbed Operation Marne Avalanche, is designed to drive out insurgents from southern Baghdad areas and prevent the flow of weapons and militants into the capital, a military statement said.

The military also said that one of its soldiers was killed on Sunday after he received wounds from an explosion while his unit was conducting operations in the northern province of Nineveh.

The latest deaths bring the number of U.S. soldiers killed in Iraq to about 3,615 since the Iraq war broke out in March 2003, according to media count based on Pentagon figures.