|Burnt car wreckage at the site of attack|
On a 6 a.m. raid, American soldiers entered Mr. Abdul-Hamid's home in western Baghdad and took him, his three sons and four guards away for questioning.
Mr. Abdul-Hamid's wife told the Associated Press that the Americans had used stun grenades, while an official from the Iraqi Islamic Party said they confiscated a computer and other items from the house.
Party secretary general Iyad al-Samarrai called the U.S. raid a provocative and foolish act that contradicted U.S. officials recent calls for full Sunni participation in the political process.
Mr. Samarrai said the Americans were putting undue pressure on the only Sunni party that calls for a peaceful solution.
Under clerical pressure, and amid fears about security, the Iraqi Islamic Party boycotted national elections on January 30.
Since then, however, it has emerged as a key player in efforts to include the underrepresented Sunni Arab community in upcoming constitutional discussions.
Mr. Abdul-Hamid, who is in his late 60s, has been involved with the party since the 1970s and is widely recognized as a moderate.
Iraq's Kurdish president, Jalal Talabani, expressed "surprise and discontent" about the arrest of a distinguished political figure, saying the presidency council was not informed prior to the U.S. raid.
While Iraq's Sunni Arab community is notoriously fragmented, both Iraqi and U.S. officials say they are eager to find representative Sunnis to help address political problems and undercut support for the ongoing insurgency.
According to the Iraqi Islamic Party, Mr. Abdul-Hamid "represents a large sector of the Iraqi people."
After interviewing him, the U.S. military decided he had been detained by mistake and released him, acknowledging his cooperation.
His brief detention came on the second day of a highly publicized anti-terrorist sweep by Iraqi army and police forces around the capital.
Operation Lightning is meant to root out the insurgents responsible for a month-long wave of car bombings since Iraq's new government was formed.
Mr. Abdul-Hamid had voiced concerns that security forces on house-to-house searches would violate the rights of innocent citizens.
Meanwhile, in Hilla, 60 miles south of Baghdad, two suicide bombers detonated themselves in succession in a crowd of police special forces troops, who were reportedly gathered outside the mayor's office to protest the disbanding of their unit.
According to police at the scene, the two bombers struck shortly after 9 a.m., setting off their explosive belts about a minute apart, and about 100 yards away from each other.
The twin blasts shattered the windows of the Hilla mayor's office, a courthouse and a school, leaving the road covered with shards of glass and rubble.
Hilla was the scene of the insurgency's deadliest single attack, as a suicide car bomber three months ago detonated his explosive-packed vehicle in a long line of police recruits.