BAGHDAD - -A bomb in a sprawling Shiite Muslim neighborhood killed at least 72 people and wounded more than 135 Wednesday, highlighting the danger that Iraq could slip into unrestrained violence after U.S. combat troops leave its cities - and with the deadline less than a week away.
It was unclear who was responsible for detonating the bomb, which was hidden in a motorcycle with a vegetable cart. Some blamed Sunni insurgents from al-Qaida in Iraq or remnants of former dictator Saddam Hussein's Baath Party, but others suggested that the bombing was the result of disputes among Shiite factions.
In either case, such bloodshed represented a major challenge for Prime Minister Nouri al-Maliki. Al-Maliki, a Shiite, has asserted that Iraqi forces are ready to take on responsibility for security with limited help from the U.S. military. His government has declared Tuesday, the deadline for U.S. troops to pull back from Iraq's cities, a national holiday.
Al-Maliki has acknowledged that there will be attacks in the days ahead but insists that Iraqi forces are up to the task. Last week, the senior U.S. commander in Iraq, Gen. Ray Odierno, expressed confidence in the Iraqi army and police.
Some U.S. soldiers are expected to remain at Iraqi bases in Baghdad and other cities as advisers, but the size of the force, rules and locations are under negotiation. President Barack Obama has set August 2010 as the deadline for U.S. combat troops to leave Iraq, and under a U.S.-Iraqi security agreement signed last year, all U.S. forces are expected to leave Iraq by the end of 2011.
Wednesday's attack occurred near rows of bird cages at the entrance to the popular Myraydi market in the Sadr City neighborhood, home to 2.5 million people, a police official said. Figures on the toll of dead and wounded were provided by medical officials. The attack followed a suicide truck bombing Saturday in Taza Khurmatu, a Shiite Turkmen town in northern Iraq, which killed at least 70 people.
The drawdown of U.S. forces, coupled with national elections scheduled for January, have raised fears that with the American presence drawing to a close, bloodshed could increase as competing factions vie for control of Iraq.
In a country emerging from sectarian war, where political parties often have ties to paramilitary groups, events such as Wednesday's bombing were certain to fuel suspicion.
Sheik Fatih Kashif Ghitaa, a Shiite cleric who runs the Al Thaqalayn Center for Strategic Studies, which has ties to the country's ruling elite, said the American effort to ease out of Iraq could end in failure.
"Now they would like to withdraw as rushed as they came," Ghitaa said this month. "Suddenly, they say, 'Build your own democracy,' when we face multiple problems: some in security, some with economics and some with corruption."
Ghitaa said armed Sunni Arab groups are bound to challenge the Shiite-led government in the months ahead. He said Iraqi officials had mostly squandered an opportunity to reconcile with former insurgents, who had turned on al-Qaida in Iraq, by failing to provide them with job opportunities.
"Al-Qaida will return to them and say, 'They gave you nothing,' " Ghitaa said.
In Sadr City, residents reeled from the blast in a market that sold pigeons, hens and geese.
"We come here every day. We sell and buy birds. It was the peak hour. Suddenly there was a huge burst of fire and smoke. I was 70 meters away. My hand was injured by shrapnel," said Haitham Ali, a 37-year-old merchant. "Most of the wounded were young men. There were women and children as well."
Market stalls were set ablaze. Volunteers carried out wounded children; some of the injured were pushed out on carts. Others had limbs blown off, Ali said.
Cement barriers, common around Baghdad neighborhoods to ward off such attacks, had been positioned around the market since April, when a pair of car bombs rocked the commercial strip.
For the past year, the Iraqi army has policed Sadr City and hemmed in radical Shiite cleric Muqtada al-Sadr's Mahdi Army militia, which once controlled the district. The bombing was likely to embolden supporters of the Shiite militia, who wish the group's fighters again would control the district.
Residents described U.S. military helicopters buzzing overhead and said that Iraqi soldiers were firing wildly after the blast.
"They are opening fire randomly in a frightening way. It's causing confusion and fear among citizens. They did the same thing after the bombing of late April and they are doing the same now," said Ahmed Majid, a 35-year-old employee at the Water Ministry. Majid accused Shiite political parties in the government of being behind the attacks.
"I'm sorry that the big bombings are coming back and accompanying the withdrawal of the U.S. forces. It seems that the Iraqi forces are unable to maintain security at all," Majid said, adding that he thought Shiite parties affiliated with Iran were behind the attack.
The district's mayor, Hassan Kareem, insisted that al-Qaida in Iraq or the Baath Party was behind the explosion.
However, a member of the district's local council, speaking on condition of anonymity, said he believed the bombing could be linked to a power struggle among Shiite factions. He refused to say which side he thought was responsible but noted that violence had been rising in Sadr City, including a spate of smaller bombings and killings.
"I'm not of the opinion the attack was Baathist or al-Qaida," the council member said. "It was Shiite."