BAGHDAD -- As the enormity of the carnage from Tuesday's deadly, synchronized bombings of Shiite pilgrims sank in, Iraqi officials and residents angrily questioned the failure of the U.S. military to protect them, even though an attack had been widely expected.

At least 143 people died in Baghdad and the holy Shiite city of Karbala, and more than 400 were injured in the deadliest single incident since the fall of Saddam Hussein last May.

'WHY HAVE YOU AMERICANS DONE THIS TO US?' Thousands of Iraqi Muslim Shiites march in Baghdad's Shiite neighbourhood of Kazimyah to protest against the US-led coalition and against the violence that hit the Shiite community on one of the most important days on their religious calendar. (AFP/Joseph Barrak)

In the grim aftermath of the twin bombings, which occurred on the Shiite holy day of Ashura, Iraqis vented their fury and grief on U.S. officials.

"It is you Americans you have done this!" said a man in the yard outside a Baghdad hospital, moments after he had found his brother lying dead inside.

Doubled over in grief with his fists balled in rage, he lurched at three U.S. military police standing nearby as his friends held him back. Other Iraqis lashed out at U.S. journalists and smashed photographers' cameras.

"Why have you Americans done this to us?" shrieked a woman draped from head to toe in black as she followed a reporter down the street near Baghdad's Kazimiya shrine, where at least 58 people were killed.

According to Baghdad police, three suicide bombers penetrated a two-ring security cordon around the Shiite shrine, entering the mosque's courtyard and detonating the explosives strapped around their waists. A fourth was arrested before his explosives belt detonated. Moments later, attackers used a suicide bomb, explosive devices and a mortar in a powerful assault on a shrine in the holy city of Karbala, killing at least 85 people. U.S. Army Brig. Gen. Mark Kimmitt insisted in a news conference Tuesday night that it was impossible to prevent every terrorist assault.

"This was a sophisticated attack, very well coordinated," Kimmitt, deputy chief of operations in Iraq, told reporters. "This was not a pick-up team."

U.S. officials said they believed the attacks had been masterminded by Abu Musab al-Zarqawi, a Jordanian widely believed to be al Qaeda's man in Iraq.

Kimmitt cited a letter ostensibly written by al Zarqawi, in which he advocates large, coordinated attacks against Iraq's religious groups in order to ignite all-out civil war. The letter was discovered by Kurdish security officials in January when they arrested an al Zarqawi associate in northern Iraq.

However, some Baghdad residents said no Muslim would dare perpetrate such a huge massacre on Ashura, revered by Iraq's 15 million Shiites and their religious brethren throughout the world. Stunned that the huge U.S. military presence in Iraq, with its impressive weaponry, had failed to protect them, some Iraqis even concluded that the Americans had turned their weaponry against their religion.

In Baghdad, a mob assaulted U.S. troops and medics who tried to control crowds and help wounded in the Kazimiya neighborhood, pelting them with stones and forcing their convoy of humvees back into a nearby walled outpost. Two soldiers suffered broken bones, and U.S. soldiers fired tear gas to disperse the crowd.

Iraq's leading Shiite political leader, Abdel Aziz al-Hakim, blamed inadequate U.S. security around the shrines for the failure to stop the attacks.

The death toll could have been higher: In the southern city of Basra, patrolled by British troops, two female suicide attackers were arrested with explosives belts, apparently on their way to blow themselves up among tens of thousands of Shiite worshipers, and two men were arrested after a car bomb was found outside the Seyed Ali al-Musawi Mosque.

In a series of increasingly deadly bomb blasts since January, a two- pronged strategy has emerged, with bombers targeting religious worshipers and Iraqi security forces.

A simultaneous double suicide attack in the Kurdish city of Irbil in early February killed more than 100 people who had gathered to celebrate the start of another Muslim festival. Last month, a suicide truck bomb killed more than 50 Iraqis south of Baghdad while they lined up outside a police station, looking for jobs in the security service. The following day, more than 50 people were killed in Baghdad by a suicide bomb detonated while Iraqis waited to apply for jobs in the Iraqi military.

Despite the recognizable pattern, Tuesday's blasts appeared to catch U.S. officials off guard. As news broke on CNN that explosions had been heard in Baghdad, a small group of reporters was meeting with a senior U.S. military official. Glancing up at the television monitor on the wall, the official initially dismissed the explosions as probably a harmless detonation of unexploded ordnance by U.S. soldiers.

He was midway through telling the journalists that attacks against U.S. soldiers fell by half between November and February -- a development that has raised Iraqis' suspicion. In numerous interviews Tuesday, Iraqis said they distrust the motivations of U.S. forces because it is Iraqis, not Americans, who are now being killed in large numbers.

"The Americans protect only themselves, not the Iraqi people," said Najim Abed, 47, near the blood-spattered Baghdad shrine.

Kimmitt said Tuesday night that U.S. commanders had opted to keep their tanks and armored vehicles well away from the shrines during Ashura for fear that the presence of U.S. soldiers would provoke Muslims during their holiest festival.

"We had cordons far away from the mosque to respect the different cultures," he said.

The few U.S. soldiers who were on patrol had only recently arrived in Iraq as part of the military's rotation of forces and were relatively inexperienced in dealing with the lethal hazards.

The toll from Tuesday's attacks also raised doubts about the plan by U.S. officials to rapidly transfer responsibility for security to Iraqi police and civil-defense units.

Iraqi police working with armed militia from the biggest Shiite political party had cordoned off the area around the Baghdad shrine, searching people as they poured in from all sides. Residents around the mosque said security had been strict.

"They were searching me for days, even though they know me well," said Ahmed Mehdi, 34, who owns a tiny store near the mosque. "But when crowds of people started arriving, anyone could smuggle themselves in."

U.S officials said last night that despite the mounting terror campaign, they would not veer from their plan to transfer sovereignty to Iraqis in four months and insisted they would keep U.S. troops in Iraq at the request of an Iraqi government.

"We will not leave, we will not withdraw until the situation has stabilized here," coalition spokesman Daniel Senor said. "So long as American forces are welcome here, and so long as there is a security need here, our forces will remain."

©2004 San Francisco Chronicle

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