BAGHDAD, Iraq – A wave of simultaneous explosions struck Shiite shrines in two Iraqi cities on Tuesday, killing at least 143 people as hundreds of thousands of pilgrims gathered for the sect's most important religious festival. Possible Al Qaeda links were being investigated.
In the bloodiest day since major combat in Iraq ended last year, three homicide bombers set off explosives in and around the Kadhimiya shrine (search) in Baghdad, killing 58 and wounding 200, Brig. Gen. Mark Kimmitt told reporters.
In the holy city of Karbala (search), at least one attacker blew himself up and pre-set explosives went off, killing 85 and wounding more than 230.
A fourth would-be bomber whose explosives did not detonate was captured at Kadhimiya, and six people were arrested in connection to the attack in Karbala, Kimmitt said.
Al Qaeda-linked Jordanian militant Abu Musab al-Zarqawi is a "prime suspect" in the attacks, Kimmitt said. U.S. officials say al-Zarqawi was planning spectacular attacks on Shiites aimed at sparking a Sunni-Shiite civil war.
In Iran, which lost at least 22 people in the attacks, the vice president for legal and parliamentary affairs, Mohammad Ali Abtahi, also blamed Al Qaeda.
Iraqi police also arrested four would-be bombers in the southern Iraqi city of Basra on Tuesday. Two men — a Syrian and an Iraqi — were arrested after a car bomb was found outside the Seyed Ali al-Musawi Mosque.
Later in the day, police arrested two women who were wearing explosives-laden belts as they marched in a procession to mark the mourning festival Ashoura (search).
A bomb was also defused Monday night in the holiest Shiite city, Najaf, officials said.
Tuesday, panicked crowds ran for safety in the streets of Karbala following five explosions shortly after 10 a.m. near two of the major shrines of Shia Islam. Karbala, 50 miles south of Baghdad, had been filled with hundreds of thousands of pilgrims marking Ashoura.
In northern Baghdad, several explosions rocked the inside and outside of the Kadhimiya shrine at about the same time. Four mortar shells landed in the shrine's courtyard as people were cooking and commemorating the holy day.
The blasts also coincided with a shooting and bomb attack on Shiite worshippers in Quetta, Pakistan, that killed 42 people.
Shiite Outrage at U.S. Troops
In Iraq, police sealed off the targeted areas as people fled screaming and ambulances raced to the scene. Dozens of armed men in civilian clothes tried to maintain order.
The attacks sparked a wave of Shiite outrage, much of it directed at U.S. troops in the Iraqi capital. American soldiers who arrived at the Kadhimiya shrine were attacked by angry crowds throwing stones and garbage, and two were injured.
In Baghdad, angry mobs hurled stones at U.S. troops who pulled into the square outside the mosque in Humvees and an armored vehicle. Crowds of enraged survivors swarmed nearby hospitals, some blaming Americans for stirring up religious tensions by launching the war, others blaming Al Qaeda or other Sunni extremists.
The explosions in both cities seemed part of a coordinated attack to coincide with Ashoura, which marks the martyrdom of Imam Hussein, grandson of the Prophet Muhammad, at the hands of Sunni forces outside Karbala. The holiday -- banned under former Iraqi leader Saddam Hussein -- draws hundreds of thousands of pilgrims from Iraq, Iran, Pakistan and other Shiite communities to the Iraqi shrines.
The religious festivals were under tight security coordinated by the U.S.-led coalition. American troops held back from the crowds, but Iraqi police were on the ground screening automobiles for explosives.
Kimmitt said that while U.S. troops usually set up an "outer cordon" around such high-security events, they stay far away from holy sites like shrines as mosques out of respect for the faithful.
U.S. intelligence officials have long been concerned about the possibility of militant attacks on the Ashoura festival. Last month, U.S. officials released what they said was an intercepted letter by a Jordanian militant to Al Qaeda leaders in Afghanistan, outlining a strategy of spectacular attacks on Shiites aimed at sparking a Sunni-Shiite civil war.
But the U.S. military decided to keep American troops, who have been a near-constant target of attacks since the end of major fighting was declared last year, out of view on the holiday to avoid aggravating Iraqis, officials told Fox News.
The attacks also came one day before the expected signing of Iraq's landmark interim constitution. The Iraqi Governing Council (search) had come to an agreement on the document on Monday, but decided to wait until after Ashoura to hold the signing ceremony.
The council announced a three-day mourning period in response to the bombings.
Mohammad Bahr Alyoum (search), this month's president of the council, said in a statement Tuesday: "We accuse the terrorists and evildoers who are obviously aiming to disrupt the unity of Iraq and destabilize the country through sectarian strife. This will not deter us from continuing our efforts to stay together and build a new Iraq. All people shall participate to build a future of happiness and prosperity."
In a show of unity, Sunni, Shiite and Kurdish council representatives appeared before journalists, calling on Iraqis to maintain calm "in order to cheat our enemies of the chance to inflict evil on the nation."
A spokesman for Grand Ayatollah Ali al-Husseini al-Sistani (search), a vocal but so far peaceful critic of the U.S.-led occupation in Iraq and possibly Iraq's most respected Shiite leader, told the Al-Arabiya television network on Tuesday that the United States was guilty of failing to protect the pilgrimage.
'We Saw Flesh, Arms, Legs, More Flesh'
Shiite cleric Sheik Sayyed Akeel al-Khatib said the explosions, "especially those at Kadhimiya," were perpetrated by homicide bombers.
"These means they came from abroad and were not were Iraqis," he told Lebanese Broadcasting Corp. TV.
The Karbala blasts struck near the golden-domed shrine where Imam Hussein is buried, in a neighborhood of several shrines. After the blasts, Shiite militiamen tried to clear the terrified crowds, firing guns into the air. Two more blasts went off about a half-hour later.
"We were standing there [next to the mosques] when we heard an explosion. We saw flesh, arms, legs, more flesh. Then the ambulance came," said Tarar, an 18-year-old, giving only one name.
Two armed Iraqi policemen broke down in tears as they walked through the bomb site.
Iraqi militia initially tried to control the crowd and arrested two men the crowd attempted to lynch. Rumors swirled throughout the city about what caused the blasts, ranging from mortars fired from outside the town to homicide bombers in the crowd.
One witness said a bomb was hidden near the mosque.
"Many Iranians were killed, I was 10 meters [yards] away, it was hidden under rubbish," one witness, identifying himself only as Sairouz, said.
Iran condemned the blasts as "terrorist" and "vicious" attacks, according to Iranian state radio. Iranian Foreign Ministry spokesman Hamid Reza Asefi said the United States and its allies were "responsible for security" for the pilgrims at Karbala and in Baghdad.
Abtahi posted a message on his personal Web site blaming the terrorist organization.
"The reactionary Al Qaeda terror group reached a conclusion ... that they have two enemies: the United States as the political enemy and Shiites as the ideological enemy."
The Baghdad blasts went off inside the Kadhimiya shrine's ornately tiled walls and outside in a square packed with street vendors catering to pilgrims. The street outside was littered with picnic baskets brought by pilgrims and thousands of shoes and sandals belonging to worshippers who had been praying inside the shrine. The courtyard inside the shrine was strewn with torn limbs.
The Kadhimiya shrine contains the tombs of Shiite saints Imam Mousa Kazem and his grandson Imam Muhammad al-Jawad.
Hundreds of gunmen swarmed inside and outside the walled shrine as men wept. A U.S. helicopter hovered overhead. Black mourning banners, traditional in Ashoura celebrations, hung in tatters. Posters of prominent Shiite clerics were stained with blood.
"How is it possible that any man let alone a Muslim man does this on the day of al-Hussein," said Thaer al-Shimri, a member of the Shiite Al-Dawa party. "Today war has been launched on Islam."
Also Tuesday, insurgents threw a grenade into an Army Humvee as it drove down a Baghdad road, killing one 1st Armored Division soldier and wounding a second. The death brings to 548 the number of U.S. service members who have died since the United States launched the Iraq war in March.
Fox News' William La Jeunesse, Jane Roh and The Associated Press contributed to this report.