BAGHDAD — A suicide 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-Qaida, suspecting the extremists want to sabotage government overtures to the Sunnis — the terror group's support base.

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.

The 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.

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.