BAGHDAD -- The U.S. military blamed a renegade Shiite militiaman Wednesday for a truck bombing that killed 63 people in a Shiite area of Baghdad, saying he was trying to reignite sectarian violence for personal gain.
The allegation points to a shift in the Iraq conflict, with the U.S. military increasingly concerned about Iranian-backed Shiite splinter groups as al- Qaida's influence recedes.
No group claimed responsibility for the blast, which devastated a bustling commercial street in Hurriyah, scene of some of the bloodiest Shiite-Sunni slaughter in 2006.
That fueled speculation Sunni extremists may have been behind the attack.
However, U.S. spokesman Lt. Col. Steven Stover said the American command believed the bombing was carried out by a Shiite splinter group led by Haydar Mehdi Khadum al-Fawadi, also known as Haydar al-Majidi, who has been sought for months for kidnapping, murder and other offenses.
"We believe he ordered the attack to incite [Shiite] violence against Sunnis; that his intent was to disrupt Sunni resettlement in Hurriyah in order to maintain extortion of real estate rental income to support his nefarious activities," Stover said in an e-mail.
A senior Iraqi security official said the investigation into the bombing was underway and that the Iraqis were not yet convinced al-Fawadi was behind the attack, the deadliest in the capital since March.
He said al-Fawadi had broken with the Mahdi Army militia led by anti-American cleric Muqtada al-Sadr, and has been running criminal operations including extortion in Hurriyah ever since.
The official spoke on condition of anonymity because he was not authorized to talk to media.
"He's a key criminal that we've been chasing for some time," said Maj. Gen. Jeff Hammond, commander of U.S. forces in Baghdad.
"We believe that he's been frustrated with the significant progress that we've made" including "the willingness of tribal leaders to move on from the attacks."
Hammond said the attack was "an effort on his behalf to try to gain some authority back."
U.S. officials have long feared that a sustained bombing campaign might reignite sectarian warfare, and some Hurriyah residents were skeptical about claims that a fellow Shiite was responsible.
"When I went to buy bread in the morning, I heard people talking," said Hurriyah resident Ayad Hussein. "Some were blaming al-Qaida. Others were blaming the Americans. It could be done by a man who has authority and could pass all these checkpoints."
Jaafar Ali, 33, a government employee from Hurriyah, suspected Sunnis in a nearby neighborhood were to blame.
"Such things always happen for political reasons," he said. "The police and army checkpoints are to blame. They have a presence there but they do not search. They have no role whatsoever."
The attack occurred about 5:45 p.m. near a bus stop and market that was packed with shoppers buying food for their evening meal. The victims included women and children, police said.