|A woman walks past a piece of a destroyed car at the site of Wednesday's bomb attack in Baghdad May 13, 2010. REUTERS/Kareem Raheem|
The minibus loaded with explosives appeared to be the latest attempt by militants to stoke a sectarian conflict by striking at a Shi'a neighborhood with strong ties to militias.
Police had initially said it was a parked car bomb, but subsequent reports revealed the minibus was moving when it exploded and three bodies were found inside, suggesting they were headed to another target inside the densely populated district of at least 2 million.
Police and hospital officials from the nearby al-Sadr and Imam Ali hospitals gave the death toll and details on condition of anonymity because they were not authorized to speak to the media.
The morning after the blast, little was left of the minibus except for a scorch mark on the spot where it exploded and a few shattered bits of the vehicle after police hauled most of it away for inspection and young boys scavenged the rest to sell as scrap in the impoverished neighborhood.
The blast also destroyed a large street sign bearing the images of anti-American cleric Muqtada al-Sadr and his revered father, for whom the neighborhood is named.
Not far away, weeping families loaded coffins on top of minibuses for the three-hour drive down to the holy city of Najaf where most of Iraq's Shi'a prefer to be buried.
Sadr City is a stronghold of al-Sadr and the scene of blasts in April that killed 72 people. Following those attacks, al-Sadr offered Iraq's security forces the aid of his militia and there have been reports it is being revived.
The Mahdi Army has clashed several times with U.S. and Iraqi forces since 2003, and was implicated in death squad-style attacks on Sunni civilians during the peak of sectarian violence in 2006 and 2007.
Experts have said that the latest wave of militant attacks, including a coordinated series of strikes on Monday that killed 119 people across 10 cities, is aimed at provoking a militia backlash and reigniting sectarian fighting.
The attacks came during a vulnerable period for Iraq.
The country has no new government after inconclusive parliamentary elections held March 7, and U.S. troops are set to cut their forces by nearly half by Sept. 1.
Iraqi security forces carried out a number of raids Wednesday following the attacks in areas around Fallujah west of Baghdad and the cities of Basra and Hillah to the south of the capital, arresting several suspects accused of involvement in the bombings.
The state-owned Al-Sabah newspaper reported Thursday that Prime Minister Nouri al-Maliki met with his top security officials and decided to replace the police commanders in the areas attacked.
Baghdad operations spokesman Maj. Gen. Qassim al-Moussawi later told a news conference that security plans in the affected areas would be reviewed. He also warned of further attacks by al-Qaeda.
Also Thursday, a roadside bomb exploded near a police patrol in Baghdad's central al-Nahda square, killing a bystander and wounding eight others, including five policemen, according to security and medical officials.