Funeral processions began Friday for the more than 200 people who were killed by car bombs and mortars in Baghdad's largest Shiite district, the deadliest attack since the war began.

Hundreds of men, women and children beat their chests, chanted and cried as they walked beside vehicles carrying the caskets of their loved ones.

Baghdad remained under a 24-hour curfew aimed at stopping widespread sectarian violence. But Iraqi Prime Minister Nouri al-Maliki, himself a Shiite, ordered police to guard the processions carrying victims of Thursday's attacks by Sunni Muslim insurgents in Sadr City to Najaf, the holy Shiite city where they will be buried.

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"God is great. There is no God but Allah. Mohammed is the messenger of Allah," about 300 mourners chanted as they beat their chests while walking through the Sadr City slum alongside slow-moving cars and minivans carrying 16 wooden caskets tied to the rooftops.

Once the processions reached the edge of Sadr City in northeastern Baghdad, the cars and minivans left most of the mourners behind for the 100-mile drive south to Najaf, a treacherous journey that passes through many checkpoints and areas controlled by Sunni militants in Iraq's so-called "Triangle of Death."

Three mortar rounds exploded Friday morning near the Abu Hanifa mosque, Sunni Islam's most important shrine in Baghdad, wounding one guard, said its sheik, Samir al-Obaidi. But the rest of Baghdad remained mostly quiet, police said.

In Thursday's well-coordinated attack, Sunni insurgents blew up five car bombs and fired mortars in Sadr City, killing at least 202 people and wounding 252 in a dramatic attack that sent the U.S. ambassador racing to meet with Iraqi leaders in an effort to contain the growing sectarian war.

Shiite mortar teams quickly retaliated, firing 10 shells that badly damaged the Abu Hanifa mosque in the Azamiya neighborhood and killed one person.

Eight more rounds slammed down near the offices of the Association of Muslim Scholars, the top Sunni Muslim organization in Iraq, setting nearby houses on fire. Two other mortar barrages on Sunni neighborhoods in west Baghdad killed nine and wounded 21, police said late Thursday.

The bloodshed underlined the impotence of the Iraqi army and police to quell determined sectarian extremists at a time when the United States appears to be considering a move to accelerate the hand-over of security responsibilities. President Bush plans to visit the region next week to discuss the security situation with al-Maliki.

"We condemn such acts of senseless violence that are clearly aimed at undermining the Iraqi people's hopes for a peaceful and stable Iraq," White House spokesman Jeanie Mamo said in Washington.

On Thursday night, Iraq's government imposed the curfew in the capital and also closed its international airport to all commercial flights. The transport ministry then took the highly unusual step of closing the airport and docks in the southern city of Basra, the country's main outlet to the vital shipping lanes in the Gulf.

Leaders from Iraq's Shiite, Sunni and Kurdish communities issued a televised appeal for calm after a hastily organized meeting with U.S. Ambassador Zalmay Khalilzad. Al-Maliki also went on state TV and blamed Sunni radicals and followers of Saddam Hussein for the attacks on Sadr City.

The coordinated car bombings -- three by suicide drivers and two of parked cars -- billowed black smoke up into clouds hanging low over blood-smeared streets jammed with twisted and charred cars and buses.

Hospital corridors and waiting rooms were awash in blood and mangled survivors of bombs that struck at 15-minute intervals in the sprawling Shiite slum.

Iraq is suffering through a period of unparalleled violence.

The U.N. said Wednesday that 3,709 Iraqi civilians were killed in October, the most in any month since the war began 44 months ago, and a figure certain to be eclipsed in November. The U.N. said citizens were fleeing the country at a pace of 100,000 each month, and that at least 1.6 million Iraqis have left since the war began in March 2003.

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