The killers came at 3 p.m. to the Daniel cloth market in the Naher district, a place that was central to Jewish commercial life in the centuries before the 1950's, when Baghdad was home to a large Jewish population. Entering the covered market, the armed men headed straight for the shops of Arab merchants selling a fabric used to make uniforms for the new Iraqi Army.

Four men were questioned about sales to the military and then shot to death, three of them in their shops and the fourth after being led out into the street, witnesses said. The killers fled.

About 45 minutes later, nearly a mile back from the river in eastern Baghdad, a Shiite cleric visiting the capital from the holy city of Karbala was shot to death in the street by men who leaped from a car without license plates. Again, the killers fled. The cleric was identified by Interior Ministry officials as Muhammad Abdul Razzaq al-Mussawi, secretary general of the Muslim Clerics' Association in Karbala, an influential group that was active in Iraq's assembly elections last month.

In other ways, Saturday was a typical day in Iraq at war.

About 9 a.m., a suicide bomber driving a German-made Opel drove up to an American armored column on a road in western Baghdad that runs past the Mother of All Battles mosque, built by Saddam Hussein to commemorate the Persian Gulf war in 1991.

The suicide bomber detonated his vehicle alongside an American M1 Abrams tank but succeeded in killing only himself and two Iraqi civilians, who later lay slumped in their shrapnel-punctured car at the scene.

The bomber caused "minimal damage," the American command said in a statement.

American military spokesmen say the tactics they have adopted to protect against suicide bombers, including shooting to kill drivers who ignore hand signals and warning shots to stay away from military convoys, have resulted in an increasing number of attacks that kill civilians but spare Americans.

In Anbar Province in western Iraq, a stronghold of the insurgents that accounts for about a third of the country's area, an American marine was killed in action on Friday, according to a Marine statement that, following standard practice, gave no details.

The marine's death raised the number of Americans killed in 48 hours to six, including three Army soldiers who died Friday when a patrol in the town of Tarmiya, 30 miles north of Baghdad, was struck by a roadside bomb.

Another car bomb exploded late Saturday morning in the Musayyib district about 40 miles south of Baghdad, killing an Iraqi soldier and wounding three others. An Interior Ministry spokesman said the bombing was directed toward an Iraqi Army raid against people suspected of being insurgents in the area around Musayyib. The district is one of a string of mixed Sunni and Shiite communities on a major highway south of Baghdad where insurgents have come under heavy pressure from American and Iraqi troops. The ministry said the raid captured 12 suspects, including a leader, whom it did not identify.

In northern Iraq, a major oil pipeline was ablaze for much of Saturday after saboteurs detonated a bomb on Friday night on a line connecting the Dibis oil fields with the city of Kirkuk, about 20 miles to the east. The attack was one of dozens that have disrupted Iraq's oil exports, costing billions of dollars and contributing to backups at gas stations across Iraq.

In Anbar Province, marines and United States Army units backed by Iraqi soldiers continued with a major operation along the Euphrates corridor, running north for more than 150 miles from the insurgent stronghold of Ramadi to a string of towns that line the river close to the Syrian border. Reuters said troops in tanks and armored cars stormed the town of Haditha on Friday night, blowing up weapons caches and exchanging small-arms fire with insurgents. In Ramadi, the hub of the area and a city strongly favored by Mr. Hussein during his quarter-century in power, fierce gun battles were said to have continued through the night.

In Haqlaniya, about 100 miles northwest of Ramadi, residents said Humvees equipped with loudspeakers drove through the town broadcasting the $25 million reward posted for information leading to the capture or killing of Abu Musab al-Zarqawi, the Jordanian who heads a militant network that has claimed responsibility for a score of bombings, kidnappings and beheadings.

The Associated Press quoted Iraq's national security adviser, Mowaffak al-Rubaie, as saying the net was closing in on Mr. Zarqawi. "We are very close to Zarqawi, and I believe that there are a few weeks separating us from him," he said.