Eight homicide bombers struck in quick succession Saturday in a wave of attacks that killed 55 people as Iraqi Shiites (search) marched and lashed themselves with chains in ritual mourning of the 7th century death of a leader of their Muslim sect. Ninety-one people have been killed in violence in the past two days.

For the second year running, insurgent attacks shattered the commemoration of Ashoura (search), the holiest day of the Shiite religious calendar, but the violence produced a significantly smaller death toll than the 181 killed in twin bombings in Baghdad and the holy city of Karbala a year ago.

The dead this year included a U.S. soldier who was killed in Baghdad when American troops responded to calls for assistance from Iraqi forces unable to cope with a slew of attacks.

With majority Shiites poised to take control of the country for the first time in modern Iraqi history, the interim government and Shiite politicians vowed the bloodshed would not cause the nation to spiral into civil war.

The homicide bombings were attempts "to create a religious war within Iraq. Iraqis will not allow this to happen, Iraqis will stand united as Iraqis foremost, and Iraq will not fall into sectarian war," Mouwaffaq al-Rubaie, the national security adviser for the interim government, told The Associated Press.

"The bombings on Shiite mosques and shrines on Ashoura by terrorists that call themselves Muslims are in fact actions by terrorists only attempting to spill even more Muslim blood by encouraging sectarian violence," he said.

The Saturday carnage was the deadliest of any day since last month's elections for a new national assembly in which the Shiite ticket, the United Iraqi Alliance (search), won 48 percent of the vote in Iraq's first democratic balloting. The alliance was expected to name its candidate for prime minister in the coming days. Forty-four people died in election-day violence.

As the violence ravaged the country, a five-member U.S. Congressional delegation including Sen. Hillary Clinton (search), the New York Democrat, met with Iraqi government officials in Baghdad's heavily fortified Green Zone.

"The fact that you have these suicide bombers now, wreaking such hatred and violence while people pray, is to me, an indication of their failure," Clinton told reporters.

Bayan Jaber, a leading member of the Shiite Supreme Council for the Islamic Revolution in Iraq, or SCIRI, said the attacks had failed to create a divide between Shiites and the Sunni Arab minority. Shiites account for about 60 percent of Iraq's 26 million people. The Sunnis make up 20 percent of the population, but dominated politics under Saddam Hussein and previous governments after Iraq gained independence from Britain.

Jaber called the attackers a small faction of Sunnis "who are extremist Wahhabis who want to spark a civil war in Iraq." But, he added, "a sectarian war will never occur in Iraq because Iraq is not like Afghanistan or Pakistan. We have tribal, marital, and historical relations with Sunnis and nothing will affect it."

The death toll built rapidly Saturday as the insurgents mounted attacks throughout the country employing homicide bombers — responsible for most deaths — mortar fire and gunmen, said Capt. Sabah Yassin, a defense ministry official.

One of the deadliest attacks was the work of a homicide car bomber at an Iraqi army checkpoint in Latifiya, 20 miles south of the capital, killing nine Iraqi soldiers.

At least seven other bombers staged attacks in Baghdad and the region. Explosions reverberated in the capital throughout the day and into the night.

It was unclear which of the attacks in Baghdad claimed the life of the American soldier. A second soldier was wounded in the assault, which also killed an Iraqi, the military said.

Insurgents appeared to have struck at will in some areas despite stepped-up security that was prompted by last year's deadly Ashoura blasts. But in Karbala, the Shiite holy city 50 miles south of Baghdad and site of one of last year's murderous explosions, no violence was reported on Saturday.

Hundreds of thousands people had gathered there to mark the holy day, which commemorates the death of the Imam Hussein, a grandson of the prophet Muhammad. Hussein was killed in a power struggle in 680 and is buried in a gold-domed shrine in Karbala.

Nearly all of Saturday's attacks inside Baghdad took place in the northern Azamiya and Kazimiya districts.

The assaults began before noon, when a bomber walked into a tent outside a Sunni mosque in western Baghdad and blew himself up, killing at least three people and injuring 10, police captain Hussain al-Ani said. About 50 people were inside the tent attending a funeral.

It was unclear why the attacker struck the tent full of Sunnis outside the Fatah Pasha mosque, but similar structures were in place outside Shiite mosques for the Ashoura celebration. Most attacks by insurgents — who are thought to be predominantly Sunni extremists — are aimed at Shiites.

Next, a homicide bomber killed two Iraqi National Guardsmen also in the north, while another homicide attacker blew himself up on a public bus in Kazimiya, killing one child and six adults. Ten people were injured.

Police officer Rashid Haroun said another homicide bomber blew himself up close to the Nada Mosque in Kazimiya and seven Shiites, including three members of the national guard, were killed. That blast also injured 55 people, he said.

According to police captain Hazim Ibrahim, two more homicide bombers died in the Kazimiya area, one who blew himself up in the Judges Institute — an academic institution — but killed no one, and another who was apparently shot dead by U.S. troops.

In other attacks, a homicide bomber blew up a car outside an Iraqi National Guard base in Baqouba, killing three Iraqi guardsmen and wounding a fourth.

Six Iraqi guardsmen were killed in a mortar attack on the main highway between Baghdad and Hillah.

Gunmen holed up in a building in Baghdad opened fire on a funeral procession as mourners carried the coffins of some of victims of a Friday bombing at the al-Khadimain mosque. Iraqi forces beat back that attack, capturing one of the assailants, said Sgt. Ali Hussein. No casualties were reported.

Yassin said eight other people were killed in unspecified insurgent violence in Baghdad and Mosul.

Also Saturday, authorities reported arresting two insurgent leaders, including a top aide to Iraqi al-Qaida leader Abu Musab al-Zarqawi, the Jordanian-born terror mastermind.

Baqouba police chief Abdel Molan said his forces had captured Haidar Abu Bawari, also known as the "Prince of the Holy Warriors." He was described as a top aide to al-Zarqawi and the man behind the insurgency in the city, about 35 miles northeast of the capital.

The Iraqi government also said it arrested one of the key insurgent leaders in the northern city of Mosul. He was identified as Harbi Abdul Khudair al-Mahmoudi, 50, also known as Abu Nor, a former member of Saddam Hussein's Baath party.