A militant group claimed Saturday that it had beheaded a U.S. Marine kidnapped last week in Iraq. The group said on a Web site that it would release a videotape showing the execution of Cpl. Wassef Ali Hassoun, but there was no confirmation that he had been killed.

Hassoun, a member of the 1st Marine Expeditionary Force, was last seen Sunday in a video aired by the Arab satellite television network al-Jazeera blindfolded and with a curved sword held over his neck. A group calling itself Islamic Response said it had captured Hassoun and would kill him unless all detainees held by the U.S. military in Iraq were freed. If carried out, it would be the third decapitation of a foreign hostage in Iraq in two months.

The report of the killing came during a new wave of violence across the country. Seven members of the Iraqi National Guard were killed in a roadside bomb attack at a checkpoint south of Baghdad, and a Marine died of wounds sustained Friday in an attack south of the capital. U.S. forces, meanwhile, raided a weapons-making facility and captured dozens of Iraqis who the soldiers said were preparing car bombs.

The Internet statement saying that Hassoun, 24, had been killed was signed by a group calling itself the Ansar al-Sunna Army. The statement said: "We would like to inform you that the Marine of Lebanese origin, Hassoun, has been slaughtered. You are going to see the video with your very eyes soon." It was not clear what connection the group had to Islamic Response.

Hassoun, a Lebanese American, disappeared from his unit in Iraq on June 19. The statement issued on Saturday said he had been lured into captivity by a love affair. The U.S. military has said that the circumstances of his absence are under investigation.

Members of Hassoun's family in West Jordan, Utah, were in seclusion Saturday, praying and awaiting official word, Shuaib-Ud Din, the imam at Khadeeja mosque in nearby West Valley City, told the Associated Press. He said he met with family members for about 15 minutes at their home Saturday, where about two dozen flags were placed in the yard in recent days. The imam cautioned the public against automatically believing reports out of the Middle East.

Al-Jazeera received a videotape Monday purportedly showing another captured American, Spec. Keith M. Maupin, 20, being shot in the head. Maupin was one of two soldiers and seven contractors who were traveling in a fuel-truck convoy on April 9 when they were ambushed with gunfire and rocket-propelled grenades in a western suburb of Baghdad. U.S. officials said they did not know whether the man shown was Maupin, and a body had not been recovered.

The handover of political authority to an interim Iraqi government on Monday, two days before the scheduled transfer, appeared to deflect the major attacks by insurgents that had been predicted last week. Iraqi officials have maintained that citizens would not fight their own government, and as the Iraqi National Guard and police units began to take over a few posts, there were signs that relative calm would prevail. There were fewer attacks, and many of those were blamed on foreigners.

The new government is searching for ways to smooth the transition and stem the violence. It plans to revive the Iraqi army and return members of former president Saddam Hussein's Baath Party to their jobs. Interim Prime Minister Ayad Allawi has said he is considering offering amnesty to Iraqi insurgents who have fought against the occupation and could possibly include those who killed Americans. The details of the plan have not been settled, but Georges Sada, a spokesman for the prime minister, told the Associated Press that if a fighter "was in opposition against the Americans, that will be justified because it was an occupation force." Sada could not be reached last night for further comment.

State Minister Adnan Janabai added: "You will see we are moving from de-Baathification to national reconciliation. Nobody willing to participate in the rebuilding of Iraq will be excluded from that."

A top U.S. military official said Saturday on condition of anonymity that there was "a sense in this country that all the attacks are being done by foreigners. But by a margin of 90 or 100 to 1, the people we detain have Iraqi passports and not foreign passports. We must admit that much of the violence in this country is being committed by people born and raised in this country."

The Iraqi National Guardsmen were killed at a checkpoint in the town of Mahmudiyah, about 15 miles south of Baghdad, at 8:30 a.m. According to Iraqi police officials, militants planted a roadside bomb near the checkpoint overnight, after guardsmen had left the site. The device exploded when the men returned, killing seven and wounding two.

Forty-five minutes later, in the southern city of Basra, a British soldier was wounded when a roadside bomb exploded. In the north, in Mosul, an Iraqi police officer was killed when insurgents opened fire on a police checkpoint.

There were conflicting reports about whether an attack caused one of Iraq's two main oil export pipelines to catch fire. Insurgents have sabotaged pipelines repeatedly to disrupt Iraq's only significant source of income. But Ibrahim Bahr Uloum, a former oil minister, said corrosion appeared to have caused the problem.

The damage to the 42-inch pipeline, which snakes through southern Iraq, reduced Iraqi exports from about 1.7 million gallons daily to about 1.2 million gallons, Uloum said. The other main pipeline was unaffected.

"The capacity is a bit low now, but within one or two days it will be back up," Uloum said.

A U.S. Army spokesman said the sweep of the bomb facility, in southern Baghdad, led to at least nine similar sites and netted weapons, rocket launchers, C-4 explosives, TNT, blasting caps, three safes containing money, and bombs in various stages of production.

Lt. Col. James Hutton called the operation a blow to anti-Iraqi forces.

"Denying the enemy of the Iraqi people the weapons he uses to kill Iraqi civilians is always a remarkable success," said Hutton, the 1st Cavalry Division's public affairs officer. Soldiers detained 51 people for questioning and said they believed they had captured key members of a group that had planted roadside bombs.

In the town of Dawr, north of Baghdad, local reports said hundreds of Iraqis staged a pro-Hussein demonstration, complete with placards and banners lauding him. The town is in a former Hussein stronghold near where he was captured last December hiding in a hole.

Meanwhile, the U.S. general who was suspended in May over allegations of prisoner abuse at Abu Ghraib prison, Brig. Gen. Janis Karpinski, told the BBC in an interview Saturday that she had met a man who told her he was Israeli who was conducting interrogations at the prison.

Karpinski said she met an interpreter who said, "I do some of the interrogation here. I speak Arabic, but I'm not an Arab. I'm from Israel."

Israel's Foreign Ministry told the BBC that reports of Israeli troops or interrogators in Iraq were "completely untrue." A top U.S. military official said he believed the claim was an urban legend evolving from the fact that one private contract employee had the surname Israel. "Nothing I have seen indicates we had anyone but government contractors and uniformed soldiers there," the official said on condition of anonymity.

Marine Cpl. Wassef Ali Hassoun has been missing since June 19.A video broadcast by al-Jazeera on June 27 showed a man identified on the video as Wassef Ali Hassoun, a U.S. Marine whom Iraqi militants claim to have beheaded.