BAGHDAD, Iraq – Shiite fighters in tracksuits and sneakers unloaded cars full of machine guns, mortars, and land mines yesterday as a five-day disarmament program kicked off in Baghdad’s Sadr City district – a sign of progress in the center of Shiite resistance in Iraq.

A lasting peace in the sprawling slum would allow American and Iraqi forces to focus on the mounting Sunni insurgency. Underscoring the threat, two American soldiers were killed in a rocket attack in southern Baghdad and a third American soldier died when a suicide driver exploded a car bomb in front of an American convoy in the northern city of Mosul.

Followers of radical Shiite cleric Muqtada al-Sadr promised the government last weekend they would hand over medium and heavy weapons for cash in a deal considered an important step toward ending weeks of fighting with American and Iraqi forces in Sadr City. Iraqi police and National Guardsmen will then assume security responsibility for the district, which is home to more than 2 million people.

In return, the government has pledged to start releasing Mr. al-Sadr’s followers who have not committed crimes, suspend raids, and rebuild the war-ravaged slum.

Members of Mr. al-Sadr’s Mahdi Army started showing up at three designated police stations early yesterday morning, carting bags full of guns and explosives – even TNT paste. Many of the weapons appeared old and rusted, but government officials expressed satisfaction with the first day’s haul.

“Sadr City residents were very responsive, and the process went without any incidents,” Interior Ministry spokesman Colonel Adnan Abdul-Rahman said.

Insurgent fighters started arriving in larger numbers once officials turned up with cash to pay them. Rates ranged from $5 for a hand grenade to $1,000 for a heavy-caliber machine gun.

If disarmament is successful in Sadr City, officials hope to replicate the process in other insurgent enclaves so they can curb resistance by nationwide elections in January.

Both sides, however, view one another with suspicion. Many rebel fighters and even some National Guard members covered their faces during the handover, apparently in fear of being targeted.

There have been several truces before with Mr. al-Sadr – none of which lasted more than 40 days. A deal brokered after heavy fighting in the Shiite holy city of Najaf in August allowed his insurgent army to walk away with its weapons. Soon afterward, clashes broke out again in Sadr City.” We made sure this time that all weapons should be surrendered,” Prime Minister Allawi said on a visit to another former insurgent stronghold, Samarra.

Elsewhere, two American soldiers were killed and five wounded in a rocket attack yesterday in southern Baghdad, the military said. No further details were disclosed. A series of heavy explosions rocked the city after nightfall.

Separately, a Turkish contractor and an Iraqi Kurdish translator were beheaded on a video posted yesterday, and a statement said they had been taken captive by the Ansar al-Sunnah Army – the same group that killed 12 Nepalese hostages.

Also yesterday, the U.N. nuclear watchdog expressed concern at the disappearance from Iraq’s nuclear facilities of high-precision equipment that could be used to make nuclear weapons.

In a letter to the U.N. Security Council, the head of the International Atomic Energy Agency said some industrial material that Iraq sent overseas has been located in other countries but not high-precision items including milling machines and electron beam welders that have both commercial and military uses.

“As the disappearance of such equipment and materials may be of proliferation significance, any state that has information about the location of such items should provide IAEA with that information,” said the agency’s director-general, Mohamed ElBaradei.

IAEA inspectors left Iraq just before the March 2003 American-led war. The Bush administration then barred U.N. weapons inspectors from returning, deploying American teams instead in what turned out to be an unsuccessful search for Iraqi weapons of mass destruction.

Nonetheless, IAEA teams were allowed into Iraq in June 2003 to investigate reports of widespread looting of storage rooms at the main nuclear complex at Tuwaitha, and in August to take an inventory of “several tons” of natural uranium in storage near Tuwaitha.

Mr. ElBaradei said that Iraq is still obligated, under IAEA agreements, “to declare semi-annually changes that have occurred or are foreseen at sites deemed relevant by the agency.” But since March 2003 “the agency has received no such notifications or declarations from any state,” he said.

As a result of the IAEA’s ongoing review of satellite photos and follow-up investigations, Mr. ElBaradei said, “the IAEA continues to be concerned about the widespread and apparently systematic dismantlement that has taken place at sites previously relevant to Iraq’s nuclear program and sites previously subject to ongoing monitoring and verification by the agency.”

Because of the holiday, American officials were not immediately available to comment on Mr. ElBaradei’s letter.