Sunni Muslims were fleeing across the Tigris River on Monday, trying to escape a four-day rampage of sectarian fighting in their Shiite-dominated home city north of Baghdad. At least 91 people have died — all but 17 of them Sunnis.

Sunnis, a minority in the city of Balad, said militiamen had been going door to door, giving them two hours to clear out of their homes, and one police officer said the bodies of the city's Sunni minority lay unclaimed in the streets.

The government and its police and armed forces appeared unable or unwilling to stop the bloodshed in Balad and its environs that may set the standard for the building inter-communal conflict should it spread further and the pace hasten, which appeared likely.

The Balad fighting exploded Friday with the discovery of the headless bodies of 17 Shiite workers in an orchard near the city, 50 miles north of Baghdad.

Shiites swiftly retaliated by setting up roadblocks in the predominantly Shiite city, ringed by Sunni-dominated villages, towns and farmland. Revenge-seekers caught, took away and shot Sunnis, guilty or not, witnesses said. All refused to give their names for fear of retribution.

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Mohamed Ali Hamid, a 35-year-old Sunni taxi driver, said he walked for two hours with 20 family members on Sunday to reach the nearby Sunni town of Duluiyah. Shiite militiamen accompanied by police gave them just two hours to leave Sunday, he said.

"They said, 'You are Sunnis and have no place here at all,"' Hamid said. "They burned everything related to Sunnis and we were forced to leave everything behind," he said by phone from a police station where he had been taken after Duluiyah law enforcement picked the group up along the highway.

Duluiyah and Balad sit on opposite sides of the Tigris River.

Ahmed Ali, a 32-year-old Sunni truck driver who was trying to reach his wife's family in Balad, said Sunni families in neighboring towns have armed themselves to fight off militia raids. He said he had been told his in-laws were killed Friday.

"Militiamen gave them just two hours to leave the house. But after half an hour, they broke into the house and killed four of them," Ali said.

A Duluiyah police officer said bodies of victims of Balad's Sunni minority lay in the streets, while the elderly and women were being forced to leave the city. The officer spoke on condition on anonymity for fear of reprisals.

About 70 percent of Balad's 80,000 people are Shiite, slightly higher than the nation as a whole. Shiite-Sunni fighting has raged increasingly out of control since a bombing in February destroyed one of Shiite Islam's holiest shrines in Samarra.

Hamid said local Sunnis had nothing to do with the beheadings and had lived in peace with their Shiite neighbors for decades. He blamed militants backed by Iran's Shiite government for the bloodshed.

"There are hidden hands behind this who want Shiites and Sunnis (to) fight each other, they are the Iranians," Hamid said.

Hamid claimed Shiite militias were seizing injured Sunnis from the Balad hospital. Both militiamen and police were roaming the town in police vehicles, brandishing their assault rifles and chanting anti-Sunni taunts, he said.

A Duluiyah police officer said members of the Mahdi Army militia loyal to anti-U.S. Shiite cleric Muqtada al-Sadr were leading the violence aided by local police.

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Scores of terrified Sunnis had fled to Duluiyah and other nearby towns, the policeman said.

An army officer at provincial headquarters said authorities have counted 74 Sunnis killed since Friday, including five who died when their houses were attacked with mortars late Sunday, said the officer, who also spoke on condition of anonymity because he was not authorized to talk to media.

The recent spike in violence also has taken its toll on U.S. forces, with the number killed so far in October surging past 50 over the weekend. Two U.S. soldiers were killed in fighting north of Baghdad, the U.S. military said, bringing to 12 the number of U.S. troops killed in Iraq since Friday.

On Monday, President Bush assured Prime Minister Nouri al-Maliki that he has no plans to pull troops out and told him to ignore rumors the United States would enforce a timeline against Baghdad.

The president's pledge came in a 15-minute morning phone call with al-Maliki, who told Bush he was concerned because he had been hearing that the United States was giving him a two-month timeline to operate on his own.

"The president didn't make any conditions, he said that we're going to support you and he said he knew that prime minister had to make tough decisions," said Bush spokesman Tony Snow. "On a number of occasions he referred to the importance of going after terrorists and militias."

Bombings in and near Baghdad, meanwhile, have killed 10 people, while 11 more bodies were found dumped in the capital.

In Suwayrah, 25 miles south of Baghdad, nine people were killed and 35 injured when a booby-trapped car exploded in a crowded market, said Mayor Hussein Mohammed al-Ghurabi.

Elsewhere, two bombs that exploded an hour apart on Baghdad's Rasheed Street killed one policeman. Iraqi insurgents have increasingly used secondary bombings to inflict further casualties on onlookers and rescue workers.

Two other roadside bomb attacks on police patrols early Monday injured seven people, and 12 people were killed or found dead in at least four other incidents in towns north of Baghdad, including a policeman slain in a drive-by shooting and four people who died when unknown assailants fired into a crowd of civilians in the small town of al-Khalis.

The bullet-riddled bodies of 11 men were found dumped in the capital overnight, two of them discovered in a trash pit in Sadr City, the sprawling Shiite slum of about 2 million people.

Each day in Baghdad brings the discovery of up to scores of such victims, most believed to have been pulled off the street or abducted from their homes by roving sectarian death squads.

Those killings have steadily worsened in recent months as the Shiite majority battles to assert its authority over the Sunni minority who held power under Saddam Hussein's former regime.