At least 172 people, many of them civilians caught in the chaos, were injured in the nearly simultaneous assaults that appeared designed to test the resolve of Washington's allies in the coalition governing Iraq.
A Polish-led force is responsible for security around the holy Shiite city of Karbala, and four Bulgarian troops and two Thai soldiers died.
In Baghdad, U.S. Army Brig. Gen. Mark Kimmitt said a total of 37 coalition soldiers, including five Americans, were injured.
Insurgents might also have targeted Karbala, south of Baghdad, on the assumption that military targets there would be more vulnerable to attack. The most intense rebel activity is in Sunni areas west and north of Baghdad, where combat-tested American troops have more experience fending off suicide bombers and other assailants.
"It was a coordinated, massive attack planned on a big scale and intended to do much harm," Polish Maj. Gen. Andrzej Tyszkiewicz said from his headquarters at Camp Babylon, east of Karbala. Poland commands a multinational force of 9,500 soldiers, including 2,400 Poles.
In an ominous note, CBS News Correspondent Kimberly Dozier says officials believe the suicide attacks, which are "a hallmark of Islamic militancy, could be a sign that Islamic extremists are now trying to fill the void left by (Saddam's followers). For Americans, that could mean a new battle for the new year."
In other developments:
One of four suicide bombers in Karbala gained entry to a Bulgarian camp, cutting through roadblocks in a car and destroying a building where the headquarters of the unit was located, Bulgarian Deputy Defense Minister Ilko Dimitrov said in Sofia.
Four Bulgarian soldiers were killed and 27 others were wounded, Dimitrov said.
"We expected these attacks because Karbala was suspiciously peaceful in the recent time," said Nikola Kolev, the Bulgarian army Chief of Staff. "We improved security measures every day but terrorists change their tactics all the time."
Bulgaria, a staunch supporter of the U.S. military campaign in Iraq, has a 485-member light infantry battalion stationed under Polish command.
A car bomb also killed two Thai soldiers on guard duty when the vehicle rammed into their camp's wall, a Thai spokesman said in Bangkok. Thailand sent 422 soldiers to Iraq in September to provide medical aid and help rebuild war-shattered infrastructure.
The Thais had been confident enough about their security that they planned to send 200 Thai civilians to visit their troops. A Thai newspaper, The Nation, said the tourists would travel with senior military officials in February. In the wake of the attacks, it wasn't clear whether the plan would go ahead.
Six Iraqi police officers and an Iraqi woman living next to one of the military bases were killed in Karbala, said Ali al-Arzawi, deputy director of the General Hospital. Some 135 Iraqi civilians and police officers also were wounded, many of them lightly, he said.
After the attacks, U.S. troops sealed off the debris-strewn area around the governor's office. Three destroyed cars lay in the street. At the hospital, crying people crowded the corridors, searching for missing family members.
"I was in the front office when I heard a loud explosion," Wahab Abdel Hussain, a 45-year-old desk officer at the governor's office, said from his hospital bed. "Shattered glass hit me in the face and then I passed out. I woke up in the hospital."
As Abdel Hussain spoke, blood ran down his face. His family sat nearby.
Mohamed Jassim, 50, said he was about to enter the governor's office to try to settle a land dispute when a car bomb exploded, injuring his hand.
"I was knocked out on the floor by the explosion," he said. He blamed supporters of Saddam, whose arrest was a major victory for U.S. troops, though American commanders believe the insurgency is a loose-knit organization without a rigid command and control structure.
Despite the attacks in Karbala, a holy Shiite city which was among the Shiite areas where Saddam conducted a bloody crackdown on opponents in 1991, U.S. military officials said the number of rebel assaults in Iraq had decreased. Kimmitt said attacks were down from about 50 a day in mid-September to an average of about 15 a day, spiking to 18 on Christmas Day.
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