Updated

Thousands of Iraqi troops moved unchallenged into Baghdad's Sadr City Tuesday to seize the Shiite militia stronghold, in the largest attempt yet by the government to impose control, an Iraqi military spokesman said.

The large Iraq force backed by tanks entered the sprawling district before dawn, with troops taking up positions on street corners and deploying on rooftops as Iraqi Humvees patrolled the streets, residents said.

• Click here to view photos.

The move is the strongest attempt yet by the government to impose control over the district, which has long been the unquestioned bastion of the Mahdi Army, the militia loyal to Muqtada al-Sadr. Iraqi and U.S. troops have in the past largely stayed on the neighborhood's edges.

The district erupted into violence in early April after an Iraqi offensive against Shiite militias in the southern city of Basra, and for weeks has been the scene of skirmishes between militiamen and U.S. and Iraqi forces.

Military spokesman Brig. Gen. Qassim al-Moussawi said the troops were deploying in the district as part of a fragile truce reached last week between al-Sadr and the government. So far, there has been no violence in the deployment, code-named "Operation Peace," he said.

"The government chose the approach of preventing bloodshed, and entered the city to coordinate with the representatives of the Sadr movement, to achieve stability and security, impose the rule of law and offer service," he told reporters in Baghdad.

• Joint Chiefs' Mullen to Congress: Iran Actions 'Directly Jeopardize' Iraq Peace

Al-Moussawi said three brigades with about 10,000 troops were involved in the deployment. He and the U.S. military said American troops were participating, though al-Moussawi said U.S. forces were nearby in case their support was needed.

The deal signed by the Sadrists and Iraq's main Shiite political bloc took effect on May 11, calling for a cease-fire that would allow Iraqi forces to take over security in Sadr City. It prohibited any attack against residential areas, government offices and the U.S.-protected Green Zone, which had faced steady rocket and mortar fire.

But the Sadrists rejected calls by Prime Minister Nouri al-Maliki to surrender weapons, saying Mahdi fighters have no "medium or heavy weapons."

Under the compromise, Iraqi forces promised to try to refrain from seeking American help to restore order. U.S. military officials said they would follow the Iraqis' lead.

The agreement gave a timeframe of gaining control as early as last Wednesday, but the Iraqis apparently needed more time to clear roadside bombs from the area along with other preparations.

The Iraqi forces in vehicles and on foot rolled into Sadr City down streets with burned out shops and buildings pockmarked with gunfire — the signs of the years of violence and clashes with U.S.-Iraqi forces that have plagued the district of some 2 million people.

Iraqi soldiers also found a large weapons cache on the grounds of the Shaaroofi mosque Monday in the Shaab district, a Shiite militia stronghold that is adjacent to Sadr City, according to a U.S. military statement.

The find included eight armor-piercing roadside bombs known as explosively formed penetrators, or EFPs, seven rocket-propelled grenades as well as other munitions and documents detailing kidnappings and murders, the military said.

The military said U.S. soldiers did not deploy around the mosque to avoid offending Islamic sensibilities.

The Sadr City operation is the latest by al-Maliki's government aimed at imposing control over areas dominated by armed groups. Besides the April sweep in Basra, Iraqi forces have been conducting a crackdown for more than a week in the northern city of Mosul, aimed at uprooting Al Qaeda in Iraq fighters and other Sunni insurgents.

Insurgents, meanwhile, targeted members of U.S.-allied Sunni groups that have turned against Al Qaeda in the volatile Diyala province.

Four anti-Al Qaeda fighters were killed by gunmen in an ambush near Duluiyah, north of Baghdad, and a 7-year-old boy was killed when a homicide bomber blew himself up near the house of the head of the so-called awakening council in Mandali, east of the capital.

Elsewhere in Diyala, shells slammed into the center of Balad Ruz, 45 miles northeast of Baghdad, killing three civilians and wounding nine others.

A bomb also exploded inside a minibus in Baghdad, killing two passengers and wounding five others.