BAGHDAD -- Dozens of fighters ambushed a U.S. patrol in Baghdad's main Shiite militia stronghold Tuesday, firing rocket-propelled grenades and machine gun bursts as the American push into Sadr City increasingly faces pockets of close urban combat.
U.S. forces struck back with 200-pound guided rockets that devastated at least three buildings in the densely packed district that serves as the Baghdad base for the powerful Mahdi Army militia.
The U.S. military said 28 militiamen were killed as the U.S. patrol pulled back. Local hospital officials said dozens of civilians were killed or wounded.
Such street battles -- in tight confines and amid frightened civilians -- are increasingly becoming a hallmark of the drive into Sadr City and recall the type of head-on clashes last seen in large numbers during last year's U.S. troop buildup in Baghdad and surrounding areas.
U.S. troops often have fought intense gunbattles as they cleared neighborhoods in Baghdad and former Sunni insurgent havens such as Anbar and Diyala provinces. But roadside bombings and rocket or mortar volleys against bases have been the more frequent mode of attack in recent years.
Meanwhile, two U.S. soldiers were killed Tuesday in northwestern Baghdad, the military said. One soldier died when his vehicle was struck by an improvised explosive device. The other died of wounds sustained when he was attacked by small-arms fire, the military said in a statement. No other details were immediately available.
Clashes have intensified in Sadr City since the Mahdi Army leader -- the anti-American cleric Muqtada al-Sadr -- reiterated his threat of an all-out war against U.S.-led forces last week. U.S. troops, meanwhile, find themselves increasingly drawn into the fight opened by the Iraqi government to cripple the power of Shiite militias.
"We are seeing larger groups of militants actually aggressively attacking Iraqi and U.S. security forces," said Lt. Col. Steve Stover, a military spokesman for American troops in Baghdad. "We've seen more of the brazen attacks in the daytime recently."
The ambush Tuesday came as a U.S. patrol of heavily armored Stryker vehicles and tanks moved along a road where the U.S. military is putting up a concrete barrier -- which seeks to cut off the militants' movements and hamper their ability to fire rockets and mortars at the U.S.-protected Green Zone.
The militia fighters struck with rocket-propelled grenades and machine guns barrages fired from alleys and rooftops, the military said.
As the troops pulled back, one vehicle was hit with two roadside bombs, Stover said. Six American soldiers were wounded.
Stover said 28 militiamen were killed when U.S. forces hit back with rockets
Officials at two local hospitals said about 25 people had died and several dozen were wounded -- most civilians. The officials spoke on condition of anonymity because they weren't authorized to release the information.
Associated Press photos showed men pulling the dust-covered body of a 2-year-old boy, Ali Hussein, from the rubble of one building.
U.S. officials said all precautions are taken to prevent civilian casualties, but blamed the militiamen for taking cover among their neighbors and families.
"The enemy continues to show little regard for innocent civilians, as they fire their weapons from within houses, alleyways and rooftops upon our soldiers," said Col. Allen Batschelet, chief of staff for the 4th Infantry Division in Baghdad.
AP Television News footage showed children running for cover behind blast walls amid gunshots. Men helped carry several blood-soaked injured people onto stretchers to a local emergency hospital. Outside the hospital, the dead were placed inside plain wooden coffins.
Also in Baghdad, a senior government official was killed in a roadside bombing in the north of the city.
Dhia Jodi Jaber, director general at the Ministry of Labor and Social Affairs, was hit by a roadside bomb as he left his home, the ministry's spokesman Abdullah al-Lami said.
Insurgents frequently target governmental officials and institutions in a bid to disrupt the government's work.
Separately, an Iraqi court adjourned until May 20 the trial of Tariq Aziz, one of Saddam Hussein's best-known lieutenants, and seven other defendants over charges of allegedly ordering the execution of dozens of merchants for profiteering half an hour after it started.
The judge postponed the trial, saying co-defendant Ali Hassan al-Majid, Saddam Hussein's cousin who is known as "Chemical Ali," was too ill to attend.
Associated Press writers Hamid Ahmed and Sinan Salaheddin contributed to this report.