The grim scene underscored fears Sunday's bloody assault on a stronghold of radical Shiite cleric Muqtada al-Sadr would plunge Iraq into another frenzy of sectarian killing.
But al-Sadr, whose directives can send thousands of heavily armed militiamen spilling into the streets, called for calm Monday and blamed al Qaeda in Iraq and the United States for the carnage.
Bomb blasts in Baghdad, Kirkuk and Tikrit — many of them targeting Iraqi police patrols — killed at least 10 more people Monday and wounded more than 30. They included a U.S. soldier killed in a roadside bombing in east Baghdad, the military said. A U.S. Marine was reported killed the previous day in the western insurgent-plagued province of Anbar.
In other developments:
Two car bombs and mortars ripped through the Shiite town of Sadr City in Baghdad, shortly before sundown, reports CBS News correspondent Lara Logan. Witnesses said people were torn to pieces in two crowded markets about a mile apart.
And it could have been worse. Police say they diffused a third car bomb.
Iraqi President Jalal Talabani said terrorists bent on igniting were taking advantage of a vacuum in authority caused by tangled negotiations to form a new government.
"The way in which this bloody act was conducted leaves us with no doubt that the terrorists have targeted this peaceful neighborhood in order to ignite civil strife and stoke the fire of civil war," Talabani said in a statement. "So, it is the duty of the political groups to accelerate efforts to form the government, and the armed forces and security bodies should act swiftly to eliminate such crimes.
Addressing reporters in the Shiite holy city of Najaf, the anti-American cleric al-Sadr avoided blaming Sunni Muslims for the attacks and appealed for unity Monday. He instead blamed the feared terror group al Qaeda in Iraq and U.S. forces.
"Sunnis and Shiites are not responsible for such acts," al-Sadr said. "National unity is required."
Sunni leaders quickly condemned the attack on Baghdad's Sadr City — named after the cleric's father, a revered Shiite leader.
Sheik Ahmed Abdul Ghafour al-Samaraie, head of the Sunni Endowment, the state agency responsible for Sunni mosques and shrines, called it "a cowardly and criminal act targeting civilians."
"There are some hands trying to add fuel to the fire for their own benefit, and the Iraqi people, Sunnis and Shiites, will be the victims," he said on local television.
The Iraqi Islamic Party, the country's largest Sunni political group, urged all parties to cooperate "in order to put an end to the bloodshed that has targeted all Iraqis of all religions and sects and to speed the formation of a national unity government that works for the security of citizens."
Members of al-Sadr's Mahdi Army militia captured the four people found hanged in the Shiite ghetto, according to police and a member of al-Sadr's organization, Sheik Amer al-Husseini. Police collected the bodies early Monday.
"We know nothing about their nationalities but residents reported that they were arrested yesterday by Mahdi Army," said local 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 the main entrances to Sadr City, and armed militiamen fanned out inside the ghetto. Fearful residents hunkered down at home, and many shops were closed.
Abdel Karim al-Bahadli, 42, wept as he hobbled on crutches to survey the devastation at one of the stricken markets. He blamed the extremist Sunni Takfiri sect of terror boss Abu Musab al-Zarqawi, leader of al Qaeda in Iraq.
"This is not resistance (to foreign occupation) because there were no U.S. troops in the markets yesterday," he said. "The Takfiris are only after Shiites. We will not be silent any more."
Young Shiite residents demanded revenge.
"The politicians call upon us to be calm, but we will not be so. Enough is enough," said Alaa Hashim, 34, who owns a neighborhood clothing store.
Iraqis had feared an attack like this one was coming, especially 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 revered Shiite shrine in the central city of Samarra.
"After Sadr City's reaction to the bombing of our holy shrine in Samarra, we were expecting bombing attacks," said Amer al-Husseini, a black-turbaned cleric who serves as an aide to al-Sadr.
The attackers struck with car bombs, including a suicide driver, and mortars at the peak shopping time, destroying dozens of market stalls and vehicles as residents were buying food for their evening meals.
The coordinated nature of the attack, and its use of a suicide bomber, bore the hallmarks of al Qaeda in Iraq, which has said it hoped to start a Shiite-Sunni civil conflict.