US aircraft and soldiers attacked Shiite militiamen accused of links to Iran on Wednesday, killing 32 and capturing 12 in a raid that coincided with Iraqi Prime Minister Nouri al-Maliki's visit to Tehran.
The Sadr City strike targeted a ring accused of smuggling armor-piercing roadside bombs from Iran, US officials said -- help that the military has said in recent days had become increasingly deadly to US troops.
Tehran has denied support for the violence in Iraq. Al-Maliki, on a state visit seeking both security cooperation and more electricity from his neighbor, had no immediate comment.
Separately, the US military said one US soldier died and four others were wounded on Tuesday by a roadside bomb in western Baghdad. Their identities had not been released.
Across Baghdad, meanwhile, devout Shiite were massing for a huge pilgrimage march yesterday, as police clamped on tight security to shield them from attacks.
The main target of Wednesday's early morning Sadr City raid was fighters from a breakaway faction of the Shiite Mahdi Army, who served as a liaison between Iraqi fighters and Iran's elite Quds Force, the US military said.
US and Iraqi forces raiding a group of buildings during the strike came under sporadic small-arms fire, killed two armed men believed to be lookouts and then detained 12 militia fighters, the military said.
US helicopters and warplanes then struck after spotting a large group of armed men on foot who were trying to attack the US ground forces. An estimated 30 militants were killed in the air attack, the US military said.
Afterward, crying neighborhood women shrouded in black accused the US of attacking civilians.
Iraqi police and witnesses said the raids had killed nine civilians, including two women, and wounded six others. A police officer and witnesses, who spoke on condition of anonymity because they feared reprisals, also said 12 people were detained.
The No. 2 US commander, Lieutenant General Raymond Odierno, has stepped up accusations against Iran in recent days, saying rogue Shiite militants aided by Tehran carried out 73 percent of the attacks that killed or wounded US troops in Baghdad last month.