US raids in the Shia district of Sadr City in Baghdad killed five and wounded at least six people.
The US military had no immediate comment on the activity in the sprawling Sadr City, a stronghold of the Mehdi Army militia loyal to firebrand cleric Moqtada al Sadr.
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Witnesses said aircraft launched strikes in the area. It was not immediately clear if there was any connection to the hunt for a US soldier who went missing earlier this week.
"We are putting all our assets into finding the soldier," said Lt. Col. Steve Stoder. "We haven't done any air strikes (in the hunt for the soldier)," he added, declining to say which areas of the city the search was focused on.
A security cordon around the central Karrada district, where troops have been searching house-to-house since the US soldier disappeared on Monday night, had been lifted today.
One witness in Sadr City said US and Iraqi troops had conducted ground raids and air strikes on a Sadr office. US and Iraqi troops had set up checkpoints around the area today and were restricting people from leaving.
A Reuters television cameraman filmed five bodies in a morgue and six people wounded, including one elderly woman, in hospital.
Two members of the Mehdi Army were believed to be among the dead.
Sunni leaders and US officials blame the Mehdi Army for sectarian killings and kidnappings that have pushed Iraq to the brink of civil war.
Washington has demanded it be disarmed and the US ambassador to Iraq Zalmay Khalilzad said yesterday it had to be brought under control.