Baghdad, Iraq ? An Iraqi militant group claimed on a Web site Saturday it beheaded a captive U.S. Marine, in what would be the fourth decapitation of a foreign hostage in the region since May.

The group, called the Ansar al-Sunna Army, posted a written statement on an Islamic Web site claiming that it had killed Lebanese-born Cpl. Wassef Ali Hassoun, saying he had been lured into a trap involving a love affair with an Arab woman.

Also Saturday, insurgents set off a roadside bomb at an Iraqi checkpoint, killing seven national guardsmen in the deadliest attack on Iraqi troops since the U.S. occupation authorities transferred power to a new Iraqi government five days ago.

Iraqi Foreign Minister Hoshyar Zebari said his country was in “a race against time” in dealing with insurgents. He said Iraqi troops were “not ready” to deal with the problems alone.

About 160,000 foreign troops, mostly American, stayed after Monday’s handover of sovereignty to the new interim government. NATO leaders last week offered military training to the new Iraqi government.

In recent days, Jordan, Bahrain and Yemen have offered military help under certain conditions.

“These countries can support United Nations operations and play a central and effective role,” Zebari said.

The U.S. military in Baghdad said it was checking into the report of the 24-year-old Hassoun’s death but had no confirmation.

It was not immediately possible to verify the authenticity of the group’s statement.

A U.S. Army 1st Cavalry soldier, left, watches over Iraqi National Guard soldiers conducting a weapons raid on a home in Baghdad, Iraq. For the first time, the 303rd Iraqi National Guard Battalion led the raid Saturday while the U.S. Army provided support.

“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,” said the statement, signed in the name of the group’s leader, Abu Abdullah al-Hassan bin Mahmoud.

It also said it had taken another hostage but did not give details.

The group called itself the Ansar al-Sunna Army in Qaim, a town on the Syrian border that has seen frequent clashes between U.S. troops and militants. The message was dated June 20, the day the military said Hassoun, of West Jordan, Utah, was first reported missing — though the posting was dated Saturday.

“We will show a new video of the detention of a new infidel hostage and as recently promised, the beheading of rotten heads,” the statement said.

“Withdraw your army and you will be safe. Or else we will keep doing what we are doing.”

On June 27, the Arab television station Al-Jazeera broadcast a videotape showing Hassoun blindfolded, along with a statement from militants threatening to kill him unless the United States released all Iraqis in “occupation jails.”

In that initial statement, the kidnappers identified themselves as “Islamic Response,” the security wing of the “National Islamic Resistance – 1920 Revolution Brigades,” referring to the uprising against the British after World War I.

Saturday’s claim on Hassoun’s death was issued on the same Islamic extremist Web forum where footage was posted last month showing the beheading of U.S. engineer Paul M. Johnson Jr., in Saudi Arabia. The site also often carries claims of attacks by Abu Musab al-Zarqawi, a Jordanian militant said to be operating in Iraq.