Baghdad ? U.S. aircraft and soldiers attacked Shiite militia bomb makers accused of links to Iran in raids Wednesday that coincided with a visit to Tehran by Iraq’s prime minister. The U.S. military said 32 suspected militants were killed and 12 were captured.

The strike in Sadr City – a major Shiite enclave in Baghdad – sought to target a ring believed to be smuggling armor-piercing roadside bombs from Iran. The precision-crafted explosives have become a growing threat to American troops, and the Pentagon has struggled to find ways to protect vehicles against their deadly power.

The sweep into Sadr City also sent a strong message that U.S. forces plan no letup on suspected Shiite militia cells despite risks of upsetting the Shiite-led government of Prime Minister Nouri al-Maliki and its efforts at closer cooperation with Shiite heavyweight Iran.

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 on the raids.

The U.S. military said 32 suspected militiamen were killed and 12 captured. But Iraqi police and witnesses said the raids killed nine civilians, including two women, and wounded six others, and made no mention of militants. They spoke on condition of anonymity because they feared reprisals.

The reason for the discrepancies in the U.S. military and local accounts was not immediately clear.

The American push into Sadr City highlighted the growing complications as more Shiite factions break apart and carve out their own agendas.

The main target was fighters from a breakaway faction of the powerful Mahdi Army, which appears to be fracturing as its leader, radical cleric Muqtada al-Sadr, loses his tight grip. The splinter group served as a liaison between Iraqi fighters and Iran’s elite Quds Force, the U.S. military said.

Across Baghdad, meanwhile, devout Shiites massed for a huge annual pilgrimage today. Police clamped on tight security to shield them from possible attacks from Sunni insurgents working to provoke an all-out civil war between Iraq’s main Muslim groups.