In Video, Al Qaeda's No. 2 Tells Bush to Admit Defeat in Iraq

"We regret to say that some voices from the Sunni organizations contributed to and justified indirectly such attacks," Hussein Shahristani, a Shiite who is deputy chairman of Iraq's National Assembly, said in an interview. "The fact that they have called on insurgents to use violence to change the results of the elections has raised a very serious question."

"I am not sure who is attacking, but I am sure that this kind of statement, this kind of cheating, will lead to violence," Saleh Mutlak, one of the country's most prominent Sunni Arab politicians, responded in a separate interview.

Thousands of angry Shiites took to the streets of Sadr City, a Baghdad slum, chanting slogans against Mutlak and the U.S. presence in Iraq, the Associated Press reported.

The State Department, meanwhile, issued a statement condemning the attacks. "Acts such as these serve only to deepen the pain and suffering of innocent people," the statement said.

Thursday was one of the bloodiest days for the U.S. military since it invaded the country in 2003. On Friday, military authorities announced the death of six Americans in Thursday's attacks, in addition to five other service members whose deaths in a roadside bombing in Baghdad had been previously reported.

Among those whose deaths were announced Friday, two of the six were killed in the suicide bombing in Ramadi. In addition, military authorities said that two Marines were killed by small-arms fire in Fallujah, and two others were killed when a roadside bomb detonated near their vehicle in Baghdad. Military authorities would not provide additional details until the soldiers' relatives could be notified.

In his Pentagon briefing, the Marines' Johnson predicted that Iraqi forces would take the principal security role in Ramadi and nearby Fallujah by mid-year, and following that in western Anbar along the Euphrates River Valley. "Probably in the next four to six months, you're going to see a number of forces who will be able to take . . . increasing lead" in Fallujah and Ramadi, he said.

Iraqi army forces in Anbar have tripled, he said, from two brigades last April to two divisions comprising nearly 20,000 soldiers. However, he said, the province's police forces, largely disbanded because of corruption and involvement in the insurgency, are being rebuilt.

Also Friday, an Iraqi police patrol found 10 bodies dumped at a site about 20 miles southeast of Baghdad, said Capt. Ahmed Sami, a police officer with the Interior Ministry. Sami said the victims, in civilian clothes, had been blindfolded, handcuffed and shot in the head.

Staff writers Ann Scott Tyson and Robin Wright in Washington and special correspondents K.I. Ibrahim in Baghdad and Saad Sarhan in Najaf contributed to this report.