BAGHDAD (AP) -- A bomb struck a municipal council building Tuesday in Baghdad's Shiite Sadr City district, killing four Americans, including two soldiers and two U.S. government civilian employees, U.S. officials said. At least six Iraqi civilians also died.
U.S. troops captured a suspect who tested positive for explosive residue after fleeing the scene, the military said. It blamed Shiite extremists for the attack.
The blast occurred at 9:30 a.m., about half an hour before a scheduled meeting to elect a chairman of the local council in the Shiite militia stronghold, an Iraqi official said, speaking on condition of anonymity for security reasons.
The bomb exploded in the office where the meeting was to have occurred, the official said, adding that at least three council members were seriously wounded.
The district council office is in a southern section of Sadr City that is largely controlled by U.S. and Iraqi troops following weeks of fighting in the area.
A U.S. military statement said one U.S. soldier was wounded in addition to the two soldier fatalities. U.S. Embassy spokeswoman Mirembe Nantongo said the American civilians included one State Department and one Defense Department employee.
U.S. Secretary of State Condoleezza Rice, in Berlin for a conference on Palestinian security, was informed of the attack shortly after it occurred and spoke with U.S. Ambassador to Iraq Ryan Crocker about the incident, according to State Department spokesman Sean McCormack.
U.S. troops sealed off the building and the area.
An official of the Iraqi Interior Ministry said six Iraqi civilians were killed and 10 others wounded. He spoke on condition of anonymity because he wasn't authorized to release the information.
The explosion occurred a day after a gunman opened fire on U.S. soldiers attending a municipal council meeting southeast of Baghdad, killing two of them and wounding three soldiers. An interpreter was also killed.
U.S. military officers have been working vigorously to restore and promote local administrations amid a sharp drop in attacks over the past year, with the goal of preventing areas from falling back under the control of rival Sunni and Shiite extremists.
Their increased presence in local communities has made them more vulnerable to attacks, but American commanders have cited it as a necessary factor in a strategy that has helped drive down the levels of violence to the lowest point in more than four years.
The U.S. military blamed "special groups criminals," a term it uses for Shiite militiamen refusing to follow a cease-fire order by anti-U.S. cleric Muqtada al-Sadr.
"This was the fourth meeting of this district council, led by hardworking Iraqis determined to make a difference and set Sadr City off on the right path. Special Groups are afraid of progress and afraid of empowering the people," said Lt. Col. John Digiambatista, operations officer with the 3rd Brigade Combat Team, 4th Infantry Division.
"They killed four people today in one cowardly act to halt progress, but it will only harden the determination of this council, the citizens of Sadr City, the Iraqi Army and Coalition Forces," he added.
The attack also targeted Americans who were attending a municipal council meeting in Madain, also known as Salman Pak, about 14 miles southeast of Baghdad.
The assailant was believed to be a former Sunni member of the municipal council. He died in a hail of gunfire after the attack, which occurred in an area with a history of Sunni-Shiite tension.
In other violence Tuesday, gunmen killed the head of the local council in Abu Dshir, a Shiite enclave in the mainly Sunni area of Dora in southern Baghdad.
Police said the council chief Mahdi Alwan was a member of al-Sadr's movement but gave no other information about a possible motive.
The U.S.-backed Iraqi military, meanwhile, pressed forward with an offensive against al-Sadr's Mahdi Army militia and other armed groups in the southern city of Amarah.
The Iraqi Defense Ministry announced a three-day deadline for all parties to voluntarily evacuate government buildings in Maysan province, of which Amarah is the capital, or face removal by force.
A provincial government official also said Iraqi security forces had begun a campaign to remove all portraits and pictures of senior religious figures from walls, buildings and the streets in the province as raids continued.
Associated Press writers Hamid Ahmed and Qassim Abdul-Zahra contributed to this report.
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