BAGHDAD, Iraq — U.S. and Iraqi forces raided a Shiite stronghold in Baghdad on Saturday, looking for dozens of men abducted from an Iraqi government office. Coalition forces searched for four American security contractors missing in an attack on their convoy in southern Iraq.

Iraqi soldiers backed by U.S. helicopters swept through the Sadr City section of the capital motivated by intelligence indicating an armed group was holding the Iraqi hostages, the U.S. military said.

The statement did not say whether any hostages were found. No casualties were reported among coalition forces, but Iraqi police said three Iraqi civilians were wounded.

Gunmen dressed like Interior Ministry commandos abducted some 150 men Tuesday from the central Baghdad office that handles academic grants and exchanges. The men were handcuffed and driven away in about 20 pickup trucks. About half were released on Tuesday night and Wednesday.

A Sunni who says he was among the hostages freed claimed the kidnappers broke his arm. He said he saw them kill at least three hostages after taking them to empty houses in the Sadr City Shiite slum.

The mass kidnapping was widely believed to have been the work of the Mahdi Army, the heavily armed militia of anti-American Shiite cleric Muqtada al-Sadr.

The kidnapping has raised questions about Prime Minister Nouri al-Maliki's commitment to wiping out the militias of his prime political backers: the Supreme Council for the Islamic Revolution in Iraq and al-Sadr's Sadrist Movement.

Sadr City has long been a Shiite militia stronghold.

In southern Iraq, coalition forces searched for four Americans and one Austrian missing since Thursday when their Kuwait-based security convoy was hijacked, said U.S. Embassy spokesman Michael McClellan.

Islamic Companies, a previously unknown group, claimed responsibility for the kidnapping, according to an Iranian-run Arabic-language satellite news station.

It said the group released a videotaped message saying it was holding the five men and demanded the withdrawal of U.S. forces from Iraq and the release of all prisoners being held there.