A homicide bomber struck Sunni and Shiite tribal leaders touring an outdoor market after a reconciliation meeting in a Baghdad suburb Tuesday, killing up to 33 people in the second major attack in the capital area in three days.

The bombings are raising fears that Sunni insurgents may be escalating operations as the U.S. phases out its combat role in Iraq and prepares to withdraw troops from cities by the end of June.

The attacks also suggest that insurgents are capable of exploiting weaknesses in Iraqi security procedures. The Iraqis have been relatively successful in curbing huge truck bombings that were common years ago — but less so against other tactics.

More than 40 people were wounded Tuesday when the bomber detonated an explosives belt as tribal leaders, security officials and journalists strolled through the market in the town of Abu Ghraib, site of the infamous prison at the center of the 2004 detainee abuse scandal.

The leaders had just left a meeting called as part of a government campaign to reconcile local Sunni tribes and Shiites who fled the mostly Sunni town on Baghdad's western outskirts two years ago but have been trickling back to their homes.

No group claimed responsibility for the attack, but U.S. and Iraqi officials blamed Al Qaeda, suspecting the extremists want to sabotage government overtures to the Sunnis — the terror group's support base.

"These are small Al Qaeda-related cells that are conducting these attacks," the top U.S. commander, Gen. Ray Odierno, told The Associated Press. "The unfortunate part is they're still able to recruit people to do this."

Iraqi police, who spoke on condition of anonymity because they weren't authorized to release the information, said 33 people died in the blast and 46 were wounded.

A military spokesman, Maj. Gen. Qassim al-Moussawi, said 29 people were killed, including at least three children. He said 41 people were wounded.

The dead included two Iraqi journalists for independent Baghdadiya TV — cameraman Haidar Hashim Suhail and reporter Souhaib Adna — as well as an Iraqi battalion commander, whose troops began firing wildly after the blast.

Four staffers for government television were wounded, one of them critically — reporter Ibrahim al-Katib, the station said. It quoted its employees as saying gunmen also opened fire from nearby buildings, sending terrified survivors scurrying for cover.

Mayor Shakir Fizaa blamed al-Qaida, saying the militants "seized on today's big meeting to carry out the attack." He also said some of the casualties were caused by the ensuing gunfire from security forces.

"This terrorist attack was aimed at stopping reconciliation and the improvement in the security situation," Fizaa told the AP. "But we will not be deterred by the acts of the vicious group against innocent civilians."

Ahmed Ali, who owns an auto repair shop in the market, said he heard someone shout "God is Great," just before the blast, then volleys of automatic weapons fire from security forces.

"I hid for a while, but then I raised my head to see scattered bodies, including women and children. Some surviving women and children were screaming out of fear," he said.

The horrific blast followed a suicide attack Sunday that killed 30 people — many of them police recruits — outside the police training academy in eastern Baghdad.

Although U.S. officials say violence has fallen to its lowest level since the summer of 2003, militants have carried out a series of high-profile attacks since last month.

They also include a March 5 car bombing that killed 13 people at a livestock market in the Shiite city of Hillah and a suicide attack against Shiite pilgrims Feb. 13 that claimed 40 lives near Musayyib.

Also Tuesday, a car bomb exploded near the municipal building in the mainly Christian town of Hamdaniya in northern Iraq, killing two civilians and wounding eight others, according to police.

The attacks suggested that Sunni extremists may have regrouped after suffering major setbacks on the battlefield and may be planning a new wave of violence as the U.S. military role fades.

The U.S. command announced Sunday that 12,000 American troops and 4,000 Britons will leave Iraq by September — the first step toward ending America's role in the war by the end of 2011.

On Tuesday, the White House downplayed any suggestions linking the recent bombings with President Barack Obama's plans to withdraw the troops.

"The previous administration negotiated and signed an agreement that ends not just our combat commitment, but our entire military commitment," spokesman Robert Gibbs said. "And I don't think that that would be done if it presented a scenario in which the country would fall into further danger."

As part of the drawdown, U.S. troops plan to withdraw from Iraqi cities by the end of June, turning over primary security responsibility to Iraqi forces.

Odierno said he does not expect the Iraqi government to ask the U.S. military to keep some forces in Iraq after the 2011 departure deadline, which was set down in a U.S.-Iraqi security agreement which took effect this year.

"I think that the Iraq leadership is focused on that this ends in 2011," Odierno said. "The progress we're making now and what I see today, I say that I don't see anything that would have us have to renegotiate in 2011."