BAGHDAD — Five car bombs exploded in and around Iraq's capital on Wednesday, killing at least 172 people and injuring more than 220 in the deadliest day for the city since U.S. and Iraqi forces launched a much-publicized security crackdown two months ago.
Four of the bombs targeted predominantly Shiite Muslim neighborhoods, sparking heated criticism of the security plan and heightening fears of revenge attacks and death squad killings.
The deadliest attack killed 140 people in Baghdad's Sadriya district, which was still recovering from a February car bombing that killed at least 130 people in a busy marketplace.
The attacks could be a setback for U.S. and Iraqi security forces, which on Feb. 13 announced an aggressive plan to deploy thousands of additional personnel in and around Baghdad.
Hundreds of new traffic checkpoints sprouted up overnight. U.S. troops increased raids on suspected insurgent strongholds, arresting 3,000 people in two months. U.S. and Iraqi officials began establishing outposts in 10 districts of the city to bolster confidence.
But insurgents have demonstrated an equal determination to undermine the crackdown. Last week, they blew up a key bridge spanning the Tigris River in Baghdad, and a suicide bomber infiltrated the tight security of the Green Zone to detonate explosives in the cafeteria of parliament, killing a Sunni Arab lawmaker.
Victims of Wednesday's late-afternoon attack in the Sadriya area included construction workers repairing buildings damaged in the Feb. 3 bombing and rush-hour commuters queuing up at a bus depot.
Survivors questioned the effectiveness of the government campaign.
"What security plan?" asked Qassim Nadhum, 40, who sells frozen meat in Sadriya and suffered shrapnel wounds to the head and shoulder. "The violence is continuing. All we get is traffic jams."
Sattar Ali, 35, a bus driver who was injured, said the crackdown appeared to work at first but that insurgents now seemed to be pushing back harder. "This is not a plan, it's just a show," he said. "It's a failure."
Baghdad police also reported finding the bodies of 17 people, apparently victims of sectarian violence. That figure combined with the toll from the car bombings made Wednesday one of the deadliest days in the Baghdad area since the U.S.-led invasion in March 2003.
The U.S. military on Wednesday reported the death of an Army National Guardsman who died of noncombat injuries Saturday at Camp As Sayliyah in Doha, Qatar. His death is under investigation, officials said.
Iraqi Prime Minister Nouri Maliki ordered the arrest and investigation of the army commander responsible for security in the Sadriya district, saying the recent car bombings there have exposed weaknesses in the system to protect residents.
U.S. and Iraqi officials urged patience, insisting that the security plan was working, while critics said the attacks demonstrated the futility of the Bush administration's policies in Iraq.
"We shouldn't expect immediate results," Shiite lawmaker Sahar Ata said. "We need to have time, at least a year."
U.S. Defense Secretary Robert M. Gates said he had warned that insurgents would attempt to ramp up the violence to derail the crackdown. He pledged to show that the plan was not a failure.
"Today was a horrifying thing," Gates told reporters in Tel Aviv. "But I think it illustrates another point: These terrorists are killing innocent men, women and children who are Iraqis."
He said the bombings appeared to be an attempt to provoke Shiite militias to retaliate.
"We can only hope that the Shia will have the confidence in their government and in the coalition that we will go after the people that perpetrated this horror," Gates said.
Congressional Democrats, who are locked in a debate with the Bush administration over a timeline for withdrawal of U.S. troops, seized on the bombings to push for a policy change in Iraq.
"They're cleaning up the mess of a marketplace that was bombed out in February. They bombed it out again today and killed about 180 people," Senate Majority Leader Harry Reid (D-Nev.) said after a meeting with President Bush to discuss war funding. "We need a new conversation about Iraq."
Administration officials expressed condolences to the families of the dead, but they noted that only three of the five brigades that had been ordered to Baghdad as part of the new plan had arrived.
White House spokeswoman Dana Perino said such spectacular attacks, and higher death tolls among American troops, are to be expected as U.S. forces move into strife-torn neighborhoods and insurgents redouble their efforts.
"Anybody who thinks that this enemy is tired, they are mistaken," Perino said. "They are a very determined enemy. They are watching what we are doing and what we are saying, and it's critically important that we finish the job in Iraq."
