(AP Photo/Khalid Mohammed)
Iraq's government blamed the attacks on supporters of Saddam Hussein "in cooperation with the al-Qaida terrorist organization" and suggested the blasts were timed for today's anniversary of the founding of the late dictator's Baath Party.
The attacks, which one Interior Ministry official called the worst breach of security in Baghdad this year, occurred as the U.S. military is drawing down its forces in the capital.
At the site of one blast, in the former militia stronghold of Sadr City, crowds hurled stones at Iraqi soldiers in a display of bitterness that they failed to prevent a car bomb from entering a busy market.
"We see nothing from them, they are useless," said Mohammed Latif, a government employee who lives in Sadr City. "They are responsible for what happened today. They are just sitting at the checkpoint doing nothing and after that they open fire randomly."
According to police, none of the six blasts claimed more than 12 lives, fewer than the 30 people who died in a March 8 suicide attack at Baghdad's police academy and the 33 killed in a suicide bombing two days later at a market on the outskirts of the city.
But the attacks Monday struck widely dispersed targets from the northeast to the southwest of the city over a four-hour period.
That cast doubt on U.S. and Iraqi claims that militants were no longer capable of the sort of mass attacks that shook Baghdad in 2006 and 2007.
No group claimed responsibility for the bombings. A U.S. military spokesman, Maj. David Shoupe, said they were believed to be "a coordinated effort" by al-Qaida in Iraq, a Sunni group, against Shiite civilians "to instigate sectarian violence."
Prime Minister Nouri al-Maliki's office said remnants of the former regime in league with al-Qaida carried out the attack to mark the April 7 anniversary of its founding.
The bombings also happened three days before the sixth anniversary of the fall of Baghdad to U.S. forces during the 2003 invasion that toppled Saddam's regime.
Some of the attacks occurred in heavily guarded Shiite areas, notably Sadr City, that Sunni extremists would find difficult to penetrate. None of the bombings appeared to have been suicide attacks, an al-Qaida hallmark.
That suggested the attackers could have been a Shiite splinter group or Baathist supporters, some of whom are Shiites.
An Interior Ministry official told The Associated Press the attacks were the most serious security breach in the capital this year. He speculated they were carried out by al-Qaida in response to a decision by Iraqi officials to remove many of the blast walls and barriers around the city.
He spoke on condition of anonymity because he feared reprisals for criticizing government policy.
Whoever was responsible, the attacks alarmed many Iraqis who are nervous about the capabilities of their security forces. The U.S. is thinning out its military presence in Baghdad in advance of a June 30 deadline for removing all American combat forces from cities -- required under the new U.S.-Iraqi security agreement.
"I fear that violence will return again to Sadr City," said Ali Abbas, a 45-year-old father of four. "Security measures in Sadr City are very weak, nearly absent."
The bombings began when a car bomb exploded about 7:30 a.m. in the center of the capital, killing six people and wounding 17, police said. Most of the victims were day laborers who gather in specific areas hoping businessmen will offer them work.
An hour later, a roadside bomb targeting an Interior Ministry convoy killed three people and wounded 12 others in east Baghdad. Less than hour later, a car bomb went off in a market in Sadr City, the former Shiite militia stronghold of northeastern Baghdad, killing 12 and injuring 37.
Twenty minutes later, another bomb exploded at another eastern Baghdad market, killing four people and wounding 20.
The final attack occurred about 11:30 a.m., when two car bombs exploded near simultaneously in an outdoor market in a Shiite area of west Baghdad, killing 12 and wounding 32.
Casualty figures came from police and hospital officials who spoke on condition of anonymity because they were not supposed to release the information.
Witnesses said police fled their posts after the Sadr City bombing. Civilians rushed to the scene to care for the victims, only to have Iraqi soldiers open fire to disperse the crowds when the troops arrived at the scene.
"We saw several people dead. Others were burned. We began to lift them and use civilian cars to take them to nearby hospitals," said Adnan al-Sudani, 37, who lives near the blast site.
"When the Iraqi army arrived, they began firing randomly" to disperse the crowd, al-Sudani said. "But angry people responded by throwing stones at them. Then the people moved away. I saw some people bleeding from the nose and the ears because of the large sound of the blast."
U.S. officials insist that violence has fallen by 90 percent since the high point in 2007, but a recent uptick in attacks has raised concern that extremists may be regrouping.
Tension has been mounting in Baghdad in recent weeks between the Shiite-led government and mostly Sunni paramilitary groups -- many of them ex-insurgents whom the U.S. organized to augment security.
Last month, Iraqi troops put down an uprising in central Baghdad by a paramilitary group angry over the arrest of their commander on terrorism and other criminal charges.
Leaders of the paramilitaries, known as Awakening Councils or Sons of Iraq, have complained that many of their followers have been arrested in recent weeks in what they fear is an attempt by Shiite officials to marginalize the Sunnis.
Also Monday, the U.S. military announced that a U.S. soldier was killed in action the day before in Diyala province, where insurgents remain active.
It was the first combat death suffered by U.S. forces in Iraq since March 16, when a soldier was killed by a roadside bomb in Baghdad.
Associated Press writers Sameer N. Yacoub and Hamid Ahmed contributed to this report.