The battle to crush a Shiite Muslim revolt in southern Iraq took on the character of a quiet manhunt overnight Wednesday, when U.S. troops seized a top aide of insurgent cleric Moqtada Sadr and tried unsuccessfully to apprehend another.

American soldiers seized Sayyid Riyadh Nouri, Sadr's brother-in-law, during a nighttime operation in Najaf, the Shiite holy city 100 miles south of Baghdad that is a stronghold of Sadr's uprising. Nouri gave up without firing a shot.

American troops also raided the Najaf home of a Sadr spokesman, Fuad Turfi. Turfi was not there, but the soldiers detained three of his brothers.

Later, Turfi said the U.S. military campaign against Sadr and his militia, the Mahdi Army, was "an attempt to destroy the patriotic spirit of the people, but they will not be able to foil our courage."

Fighting between U.S. forces and the Mahdi Army continued Wednesday in Najaf, where American soldiers bombarded a vast cemetery that Sadr's militia uses to stage attacks on U.S. patrols. Rocket fire from U.S. attack helicopters left two craters in a road that bisects the cemetery and sprayed tombstones with shrapnel.

Officials at Najaf Hospital said eight people died in the fighting, including an elderly civilian and a child. A Sadr spokesman, Qais Khazali, put militia fatalities in the dozens.

Meanwhile, the U.S. Marines said in a statement that three Marines were killed "while conducting security and stability operations" in the western province of Anbar. And two Russian civilians and their Iraqi driver were killed by attackers in Baghdad.

The conflict with Sadr has persisted for six weeks in a half-dozen cities in Iraq's Shiite-populated south and in parts of Baghdad. Occupation officials and military commanders want to put down the insurgency and capture Sadr, who is wanted on a warrant issued by an Iraqi judge in connection with the killing of a rival cleric a year ago.

But U.S. officials have expressed concern that continued fighting could broaden sympathy for Sadr among Iraq's Shiite majority, which has grown mistrustful of U.S. claims of an intent to bring democratic rule to Iraq.

Though fighting this week has been largely confined to Najaf and the adjoining town of Kufa, clashes also have broken out in the past few days in Sadr City, the vast Shiite slum in Baghdad named for Sadr's slain father. Associates of Sadr said two Mahdi Army fighters were killed when they attacked a U.S. patrol there Wednesday.

"We are constantly chipping away at his militia, his illegal militia," said the chief U.S. military spokesman in Iraq, Brig. Gen. Mark Kimmitt.

Kimmitt rejected reports Tuesday that U.S. troops in Karbala, another Shiite holy city, blew up the Mukhaiyam mosque, where Sadr's forces stored arms. Soldiers did, however, find weapons in a nearby building and destroyed them with explosives, he said.

Meanwhile, a member of one of Iraq's biggest and best-organized Shiite political parties said Sadr had agreed to convert the Mahdi Army into an unarmed movement, return seized government buildings and surrender to an Iraqi court after June 30, the date set for the transfer of limited authority to a new Iraqi government. In return, Sadr wants his movement to take part in elections, said Adnan Ali, a member of the Dawa party.

Ali said Sadr made the offer in writing and that it was delivered to the Coalition Provisional Authority, the U.S.-led occupation administration. The occupation authority has not responded, Ali said in an interview in Baghdad.

A senior occupation official said the authority had nothing in hand from Sadr that it considers a significant offer. However, Shiite politicians are engaged in intense talks with the firebrand cleric over ways to end the insurgency, he said, adding that the talks could bear fruit in "the next few days."

"Clearly," the official said, "the reverses Sadr has suffered have had an impact."

Kimmitt said he knew nothing about a new offer from Sadr and expressed skepticism. "We have heard this kind of thing so many times. There have been so many attempts," he said. "So many of these offers turn out to be just someone looking for a day in the sun."

While the conflict between occupation forces and Shiite insurgents has largely played out in head-to-head military confrontations, Sunni Muslims around Baghdad and in western Iraq continue to battle the occupation through hit-and-run ambushes, roadside bombings, suicide car bombings and occasional rocket and mortar fire. The Sunni insurgents also have carried out a campaign of killing Iraqis who cooperate with U.S.-led authorities and foreigners working in Iraq. On Wednesday there were examples of both.

A gunman in an Opel sedan sprayed automatic-rifle fire at a bus carrying Russian electrical engineers to a power station in the Baghdad suburb of Daura, killing two Russians. The gunman and his driver then stopped and slit the throat of the Iraqi bus driver, killing him, witnesses said.

Five wounded Russians were treated at Yarmouk Hospital. Their company, Moscow-based Interenergoservis, decided to withdraw its remaining employees from the country, news service reports from Russia said.

Workers from the same company were ambushed south of Baghdad on May 10. One Russian was killed and two were taken hostage. Last month, insurgents captured eight Interenergoservis employees but set them free in a day.

"It's just too dangerous now, far too dangerous," said a survivor of Wednesday's attack who identified himself as Gennady. Iraq's electrical infrastructure is partly of Soviet origin, and the Russians were brought in to renovate it.

In Baqubah, a volatile town northeast of Baghdad, gunmen ambushed the chief of police of the nearby city of Khalis, killing both him and his driver, Kimmitt said.

Fifty miles north of Baqubah, a roadside bomb detonated next to a passing convoy that included the car of the police chief of the town of Balad Ruz. He escaped uninjured, but five other people were killed.

Special correspondent Saad Sarhan in Najaf contributed to this report.

A Russian electrical worker is hospitalized in Baghdad after an attack on a bus killed two colleagues and an Iraqi driver and wounded four others.