Rumors of a suicide bomber sowed panic among thousands of Shiite Muslim pilgrims Wednesday on a bridge over the Tigris River in Baghdad, triggering a stampede in which many jumped into the turbid river or fell to their deaths on sidewalks and a children's playground below.

The Iraqi Health Ministry on Thursday put the death toll at 843. The Interior Ministry said 953 people were killed and 815 injured, the Associated Press reported. Bodies of victims had been taken to many hospitals, mosques and private homes, making an accurate count difficult.

The disaster took more lives than any other single incident in Iraq since the U.S.-led invasion in March 2003. Tensions had been high among the pilgrims, who were marching to Baghdad's Kadhimiyah shrine, because of an insurgent rocket and mortar barrage earlier in the day that killed seven worshipers. Survivors and security officials placed much of the blame for the stampede on securi- ty checkpoints set up at the entry to the bridge that narrowed foot traffic to one or two people at a time so that guards could search male pilgrims for explosives.

In a twist for a nation increasingly besieged by sectarian rivalries, survivors and rescuers credited residents of a hard-line Sunni Arab neighborhood with helping to save the lives of countless Shiites. Witnesses said Sunnis from the Adhamiyah district waded into the Tigris to pull Shiites from the water and helped haul them to safety. Adhamiyah, where President Saddam Hussein made his last public appearance after the invasion, was one of the last neighborhoods in Baghdad to stop fighting occupation forces in 2003 and is still a stronghold of Baath Party loyalists.

"Adhamiyah saved them," said Ahmed Abdullah Hussein, a 62-year-old auto mechanic.

Some rescuers said the majority of victims suffocated on the bridge. "Their faces were black, black like this tire," Hussein, a Sunni, said at his repair shop, located in the shadow of the bridge.

Mariam Abbas, 22, a small, round-faced woman in a black veil, survived the crush on the bridge. "You felt your body would collapse; you could not breathe,'' she recounted.

Abbas said she clasped the shoulders of a young man beside her in a desperate attempt to lift herself high enough out of the throng to gasp air into her lungs. "Some people jumped from the bridge -- old men, young people, kids," she said.

As Abbas began losing consciousness, she said, she felt the grasp of a stranger who saved her.

"He grabbed me by my arms and held me up, and threw me down to his friends below the bridge," Abbas said. Her Sunni rescuers gently splashed water on her face to revive her. "They said, 'Are you okay?' And then they ran to help others."

Adhamiyah residents took hundreds of people, most of whom were mortally injured, to a Sunni mosque, a Sunni hospital and Sunni homes. Bystanders brought corpses to hospitals overflowing with the dead; many bodies were placed outside on sidewalks.

Prime Minister Ibrahim Jafari declared three days of national mourning for the victims, most of whom were women, children and old men, all too weak to survive the crush of the crowd, witnesses said.

Government ministers traded blame for the disaster, with some suggesting the tragedy was caused by insurgent sabotage. Jafari, a Shiite, cited rumors that pilgrims had been poisoned by juice given to them as they walked through the Sunni district.

Throughout the day, crowds estimated at more than 1 million streamed toward the Kadhimiyah shrine, which sits atop the 9th-century grave of Moussa Kadhim, the seventh of 12 imams revered by mainstream Shiites. Such public Shiite religious observances, banned during the rule of Saddam Hussein, have drawn vast crowds in the past two years and have been regular targets of insurgent bombings that have killed hundreds of worshipers.

The stampede began near the east end of the bridge, which links Adhamiyah to a Shiite neighborhood on the other side of the river. Crowds going to the shrine were backed up at the concrete checkpoints, while throngs of those returning from the shrine tried to push past in the other direction.

"More than one person started yelling and saying, 'The bridge will fall down! The bridge will explode!' " said Khalid Fadhil, a goldsmith who witnessed the stampede. "So the people started running in panic, pushing each other, trying to run away.

"Some of the people fell down, and the people stepped on them. The others threw themselves off the bridge, into the river."

Some of the pilgrims at mid-span plunged more than 90 feet into the Tigris.

"Whoever was able to swim and knew how to swim survived. The people who didn't know how died," said Sattar Jabbar, 22, a black-clad member of the Mahdi Army, the militia loyal to Shiite cleric Moqtada Sadr, which helped provide security for the pilgrimage.

Others closer to the end of the bridge who jumped slammed to their deaths on the ground below.

"I saw an old woman who was completely panicked and crying throw herself from the bridge," Fadhil said. "I saw another man fall on the bricks of the shore and die immediately. I saw seven people were brought dead near the end of the bridge, smothered.

"Other people were running and shouting, 'God is great! God is great!' " Fadhil said.

Rubber sandals, bundles of food and knots of twisted clothing collected, along with bodies, on the playground and the concrete beneath the bridge. Shoes piled up in layers on the bridge above, their owners injured or dead.

The swirl of pilgrims being crushed underfoot and bodies slipping from the bridge stretched on for several long minutes, witnesses said.

Residents of Adhamiyah wrenched out the monkey bars and the seesaws of the playground and propped them against the bridge so pilgrims could clamber to safety, witnesses said.

Ahmed Hussein and other residents of the neighborhood rushed from shops and homes to help.

"We ran with pickups, cars, anything that we can use to carry the bodies. The number of cars were too few for the big number of people," Hussein said. "We put women on top of men on top of children, on every car."

Others pulled mattresses from their beds to carry the victims, he said. "We carried, not knowing if they were dead or alive," he said.

Jabbar, the militia member, "jumped into the river to save people -- anyone," he said. The first person he found was a man. "His face was green, and I found him dead. I left him, looking, trying to save someone."

Fadhil, the goldsmith, described watching a Sunni sheik take to the river in a small armada of motorboats and rowboats to help pull victims to shore.

Two hours earlier, several mortar and rocket rounds had hit the area around the Kadhimiyah shrine, killing seven people and injuring at least 40. U.S. Apache helicopters fired on the attackers, the military said in a statement.

By late afternoon, security workers on the bridge restored an orderly flow of pedestrians coming and going from the shrine.

"Too late," said one pilgrim, who identified himself only as Hussein. "After the disaster, they did this."

Also Wednesday, the U.S. military announced the deaths of two soldiers in separate attacks. One was killed by a roadside bomb Tuesday in the city of Iskandariyah in central Iraq. The other was killed and three soldiers were wounded when a bomb exploded Wednesday next to their patrol near the town of Samarra, north of Baghdad.

Special correspondents Bassam Sebti and Omar Fekeiki contributed to this report.

A man at a Baghdad hospital finds the body of his brother, who was among hundreds killed in a stampede sparked by rumors of a suicide attack.Piles of shoes on a Baghdad bridge provide an eerie reminder of the stampede. Most of those killed were women, children and elderly men, witnesses said.