A car bomb struck a bakery crowded with customers lining up for bread, killing at least 11 people on Saturday as they ended their daytime Ramadan fast, officials said.

An al-Qaida front group, meanwhile, warned it will hunt down and kill Sunni Arab tribal leaders who cooperate with the U.S. and its Iraqi partners, saying the assassination of the leader of the revolt against the terror movement was just a beginning.

Hospital officials said the 11 killed in the Baghdad explosion included two children. The blast damaged five stores and three houses and burned five cars, according to police.

"We rushed outside the house after hearing the sound of the explosion. I could see the bakery and a nearby pickle shop on fire," said Abu Ahmed, a 36-year-old Shiite government employee. "The wounded were screaming for help as the ambulances were arriving."

The bombing, which occurred at the start of iftar, the meal Muslims eat to break their dawn-to-dusk fast during the Islamic holy month of Ramadan, was a blow to Iraqi government hopes that it would be a peaceful month to show the success of a 7-month-old security operation in the capital and surrounding areas.

Al-Qaida statements were posted Friday and Saturday on Islamist Web sites and among other things claimed responsibility for the assassination of Abdul-Sattar Abu Risha, who spearheaded the uprising against al-Qaida in Anbar province west of the capital.

In claiming responsibility for Abu Risha's death Thursday, the Islamic State said it had formed "special security committees" to track down and "assassinate the tribal figures, the traitors, who stained the reputations of the real tribes by submitting to the soldiers of the Crusade" and the Shiite-led government of Prime Minister Nouri al-Maliki.

"We will publish lists of names of the tribal figures to scandalize them in front of our blessed tribes," the statement added.

In a second statement posted Saturday, the purported head of the Islamic State, Abu Omar al-Baghdadi, said he was "honored to announce" the new offensive in memory of al-Zarqawi.

"Today we witness the fallacy of the Western civilization and the renaissance of the Islamic giant," al-Baghdadi said in a half-hour audio file.

U.S. officials hope Abu Risha's death will not reverse the tide against al-Qaida, which began last year when he organized Sunni clans to fight the terror movement, producing a dramatic turnaround in Ramadi and other parts of Anbar province.

The revolt has spread to Sunni insurgent groups in Baghdad, Diyala province and elsewhere. Some insurgents who were ambushing U.S. troops a few months ago are now working alongside the Americans to rid their communities of al-Qaida.

Abu Risha's brother Ahmed was elected head of the Anbar Awakening movement soon after the bombing at the family's heavily guarded compound on the outskirts of Ramadi.

The national Interior Ministry announced that a police brigade would be named after the slain tribal leader and a statue would be erected in Ramadi in his honor.

Iraqi officials said the roadside bomb was just outside Abu Risha's walled compound in view of a guard shack and an Iraqi police checkpoint.

Lt. Gen. Raymond Odierno, the second-highest ranking U.S. officer in Iraq, and several high-ranking government officials attended the funeral, including Iraq's interior and defense ministers and National Security Adviser Mouwaffak al-Rubaie.

"We condemn the killing of Abu Risha, but this will not deter us from helping the people of Anbar — we will support them more than before," al-Rubaie declared. "It is a national disaster and a great loss for the Iraqi people — Abu Risha was the only person to confront al-Qaida in Anbar."

Abu Risha's assassination clouded President Bush's claims of progress in Iraq, especially in Anbar, which had been the center of the Sunni insurgency until the dramatic turnaround by the local sheiks. Bush met with Abu Risha during a visit to Anbar on Sept. 3.

In a televised address Thursday, Bush ordered gradual reductions in U.S. forces in Iraq but rejected calls to end the war. More than 130,000 U.S. troops will remain after the withdrawals are completed in July.

Defense Secretary Robert Gates on Friday raised the possibility of cutting U.S. troop levels to 100,000 or so by the end of 2008, if conditions improve enough.

"It was encouraging to see the president's comments to Americans to reinforce support for us," said U.S. Lt. Col. Mike Donnelly, 42, based at Tikrit with the 25th Infantry Division.

U.S. Capt. Bryan Greening, 25, said he found no surprises in Bush's speech.

"I think the drawdown is a good idea," said Greening, assigned to Tikrit with the 1st Cavalry Division. "The surge has done whatever it can and now it's time to allow soldiers to go home and get some rest."

1st. Lt. Larry Pitts, 33, serving with the 82nd Airborne Division in north Baghdad, said soldiers are aware of the political debate in the U.S. but "we don't have the time to worry about the big picture."