Baghdad, Iraq ? Shiite Muslim militiamen rampaged through a Sunni Arab neighborhood in Baghdad early Sunday morning, killing more than 50 people and discarding bodies in the streets, according to Iraqi officials and witnesses. Hours later, attackers struck back, detonating two car bombs near a Shiite mosque.

Sunni politicians described the violence against the Sunni residents of the al-Jihad neighborhood in western Baghdad as one of the most cold-blooded murder sprees since the U.S.-led invasion in 2003.

The killings occurred on a day when the U.S. military announced charges against five soldiers in the alleged rape and murder of a girl and the killing of three members of her family in the southern Iraqi town of Mahmoudiya.

Sectarian killings escalated sharply across Iraq after a bomb destroyed a revered golden-domed Shiite shrine in Samarra on Feb. 22. The bombing prompted reprisal attacks on Sunni mosques and pushed the country further toward all-out civil war.

In Baghdad, the armed men, some wearing masks and dressed in black, descended on the al-Jihad neighborhood in buses after sunrise. They set up checkpoints along a main commercial street, demanded identification cards from passersby and burst into homes to single out Sunni Arabs to kill, residents said. One resident, Hazim al-Rawi, said he gathered up his family and fled the neighborhood after he saw 15 bodies outside his home.

A mother cries over her young boy wounded in crossfire during street fights Sunday in the al-Jihad area of western Baghdad, Iraq. Gunmen stopped cars and burst into homes in western Baghdad, singling out Sunni Arabs and killing at least 50 people, police said.

“Some of them were tortured with drills,” he said of the bodies. “Some of them were hanged by ropes.”

A U.S. military spokesman said that Iraqi national police and American soldiers found 11 dead Iraqis in three locations in the neighborhood. The higher casualty reports “do not marry up with what we have found,” Lt. Col. Jonathan Withington said.

Still, Sunni politicians said the spate of attacks killings gravely exacerbated the problems in Baghdad, where killings occur almost daily, and they accused Iraqi police of collaborating with Shiite militiamen in the violence.

“This is a new step. A red line has been crossed,” said Alaa Makky, a Sunni member of parliament. “People have been killed in the streets; now they are killed inside their homes.”

Attackers retaliated by detonating two bombs in cars parked at al-Timim Shiite mosque in central Baghdad. At least 12 people were killed, including five policemen, and 18 were wounded, according to Lt. Col. Memduh Abdulla of the Rusafa police district. The Associated Press reported that 17 people were killed and 38 hurt.

“We’ve said it several times that there are people who want to create civil war,” Wafeeq al-Samarrae, an adviser to Iraqi President Jalal Talabani, said on the al-Jazeera satellite television network. “Today, this country is on the edge of civil war, not sectarian strife.”

Police picked up 57 bodies from the al-Jihad neighborhood, and three Interior Ministry police were also killed there, said Ali Hussein, a commando with the Interior Ministry who ferried bodies to Baghdad’s Yarmouk Hospital. Gen. Saad Mohammed al-Tamini of the Interior Ministry confirmed that more than 50 people were killed.

Some of the corpses that littered the streets lay handcuffed, pocked with bullet holes, while others were pierced with bolts and nails, witnesses said.

Iraqi officials and residents of the neighborhood identified the gunmen as members of the Mahdi Army, the powerful militia controlled by the radical Shiite cleric Muqtada al-Sadr. In the past three days, Iraqi troops, with the support of U.S.-led forces, have raided the homes of militiamen and detained some of their leaders.

U.S. commanders and diplomats say Sadr and his militia constitute one of the gravest threats to Iraq’s security. Two years ago, U.S. forces fought Mahdi Army militiamen in Baghdad and in the southern holy city of Najaf. Sadr also holds considerable sway over the political system, with ties to more than 30 members of parliament and several cabinet ministers.

On Sunday, Iraq’s deputy prime minister for security affairs, Salam al-Zobaie, accused the Defense and Interior ministries of working with the militias to carry out the killings.