Baghdad, Iraq ? Scorched pavement, destroyed shops, burned-out cars and four men shot in the head then hanged from electricity pylons – victims of revenge killings – awaited Shiite residents emerging from their homes Monday in Baghdad’s Sadr City slum.

The scene, although gruesome, was not what many had feared: That deadly explosions the previous night in Sadr City would ignite all-out civil war, pitting majority Shiites against minority Sunnis.

Two car bombers and four mortar rounds shattered shops and market stalls at nightfall Sunday when residents were buying groceries for their evening meal. At least 58 people were killed and more than 200 wounded.

A key to Monday’s relative peace was anti-American cleric Muqtada al-Sadr’s refusal to be provoked. With thousands of his Mahdi Army militiamen ready to fight, the Shiite leader called for calm and national unity. It was the second time in less than three weeks that Iraqis stood at the precipice of civil war but pulled back.

Bomb blasts and shootings in Baghdad and north of the capital, many of them targeting Iraqi police patrols, killed at least 15 people Monday and wounded more than 40. They included a U.S. soldier who died in a roadside bombing, the military said. A U.S. Marine was reported killed Sunday in insurgent-plagued Anbar province.

The American deaths brought the number of U.S. military members killed to at least 2,308 since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Iraqis view burnt out cars at the site of the bomb explosions in Shiite district of Sadr City, in Baghdad, Iraq, Monday, March 13, 2006. The feared resumption of mass sectarian violence erupted in a Baghdad Shiite slum when bombers blew apart two markets shortly before sundown, killing at least 44 people and wounding about 200 on Sunday. The bloody assaults on Sadr City came only minutes after Iraqi political leaders said the new parliament will convene Thursday.

Police and Sheik Amer al-Husseini, a senior aide to al-Sadr, said the four men shot and hanged in Sadr City were captured by members of the cleric’s militia. Police said they cut the bodies down and took them to a hospital morgue Monday morning.

“We know nothing about their nationalities but residents reported that they were arrested yesterday by Mahdi Army,” said police Lt. Laith Abdul-Aal. “Two of them were wearing explosive belts and two others had mortar tubes.”

Al-Husseini identified the men as three Iraqis and a Syrian.

Iraqi police manned checkpoints Monday at main entrances to Sadr City, and armed militiamen fanned out inside the neighborhood. Many people ventured out only to buy food.

Sadr City residents had feared an attack like this one after al-Sadr’s fighters stormed out of the slum to take revenge on Sunni Muslims and their mosques after the Feb. 22 bombing of a Shiite shrine in Samarra.