A militant group claimed Tuesday to have killed a second American contractor held hostage in Iraq, according to a statement posted on an Islamic Web site.

The claim, which was reported by the al-Jazeera television network and news services, could not be independently confirmed.

The reported killing of Jack Hensley, a civil engineer from Marietta, Ga., came less than 24 hours after kidnappers released a grisly video that appeared to show the beheading of Hensley's American co-worker, Eugene "Jack" Armstrong.

The two Americans and a British contractor, Kenneth Bigley, were seized in Baghdad Thursday by militants believed to be led by Jordanian-born militant Abu Musab Zarqawi. The three contractors were working in Iraq for Gulf Supplies and Commercial Services Co. of the United Arab Emirates.

The statement claiming that Henley was killed was posted in a message on an Islamic Web site by someone using a pseudonym, Abu Maysarah al-Iraqi, who has posted previous online messages on behalf of militants, the Reuters news agency reported.

According to Reuters, the message said the kidnappers "have slaughtered the second American hostage" and that "the British hostage will meet the same fate if the British government does not do what must be done to release him."

The militants who kidnapped the three contractors have demanded the release of Muslim women held at two prisons: Abu Ghraib west of Baghdad and Camp Bucca, near Umm Qasr in southern Iraq. U.S. military officials say that only two women are being held in Iraq and that neither is confined at those prisons. The two women, Rihab Taha and Huda Salih Mahdi Ammash, allegedly were part of ousted president Saddam Hussein's program to develop biological weapons.

On Saturday, the kidnappers threatened to begin executing the men within 48 hours if their demands were not met. On Monday, the Zarqawi group posted a video on the Internet showing what it said was the beheading of Armstrong, a Michigan native. A U.S. official in Washington confirmed that a body believed to be Armstrong's had been recovered.

Before the reports of Henley's possible killing on Tuesday, family members of the two remaining hostages appealed for their lives.

Hensley's wife, Patty Hensley, appeared early in the day on ABC's "Good Morning America" to ask again that her husband be spared. "My daughter would like her father back and I'm willing to do whatever it will take to get him here," Hensley said.

"We are putting a lot of strength in our belief that Jack was honestly there to help the people and because of that they should not harm him and hopefully will not," she added.

In an interview with the Associated Press, she said that "All of my appeals through the media are to the captors, saying please re-open up the lines of communication with us and to give us an opportunity to explore exactly what you are looking for. . . . I am willing to do whatever it will take to get him here."

Asked whether she had had contact with the kidnappers, Mrs. Hensley said it had been a one-way discussion. "I don't feel like there has been an open line between any of the agencies or anybody in trying to communicate further."

The nine-minute video released Monday showed Armstrong blindfolded and seated in an orange jumpsuit in front of five masked men, four armed with assault rifles. Behind the black-clad militants was the black-and-white banner of Zarqawi's militant group, Jamaat al-Tawhid and Jihad (Monotheism and Holy War), which has asserted responsibility for the beheadings of other hostages, including an American contractor, Nicholas Berg, in May and a South Korean driver, Kim Sun Il, in June.

Patty Hensley told the AP that she had spoken to the Armstrong family several times since the killing of Eugene Armstrong.

"They are still in a great deal of shock and of course their prayers are now going out for Jack and Ken Bigley," Hensley said. "They still don't understand why. These were three very kind, benevolent men who were just trying to help the Iraqi people. They had no hidden agendas for why they were there."

She told the AP that she spoke to her husband probably 45 minutes before he was taken and they were trying to work out why his security was no longer around. "It was hard to determine when this was a real issue or not. Unfortunately, it was a very real issue," she said.

British Prime Minister Tony Blair spoke to Bigley's family Tuesday, following an appeal by Bigley's son for the government to yield to the kidnappers' demands. Bigley's son Craig, speaking on BBC TV, urged Blair to "meet the demands . . . two women for two men. . . . Only you can save him now. You have children and you will understand how I feel at this time."

Meanwhile, a Turkish construction company announced Tuesday that it was halting operations in Iraq in a bid to save the lives of 10 employees kidnapped by militants, news services reported.

The Ankara-based VINSAN construction company said in a statement it was freezing operations and added that its kidnapped employees were innocent and were trying to support their families, the AP said.

In a video broadcast Saturday by al-Jazeera television, a previously unknown militant group calling itself the "Salafist Brigades of Abu Bakr Al-Siddiq" said it would kill the 10 hostages if the company did not pull out of Iraq within three days. Most of the 10 hostages were truck drivers, according to the company.

The firm was one of 21 international companies taking working on a road project in Iraq.

A number of Turks have been kidnapped and several have been killed, and at least seven Turkish companies have withdrawn from Iraq to secure the release of kidnapped staff.

In other developments Tuesday, the military announced that two U.S. soldiers are being investigated in connection with the wrongful deaths of three Iraqis.

A statement from the 1st Cavalry Division said charges had been preferred against the soldiers, both members of Task Force Baghdad. No further information was provided.

"The Army's Criminal Investigation Division (CID) is currently investigating the allegations. The events relating to these charges cannot be discussed in detail at this time due to the on-going investigation," the statement said.

Army investigators have launched several probes into the wrongful deaths of Iraqis since the invasion to overthrow President Saddam Hussein last year. Some have related to the death of prisoners being held at U.S.-run detention facilities, others to civilians killed while U.S. troops were on operations.

In addition, Britain's civilian authorities have charged one British soldier with murder over the killing of an Iraqi civilian in August 2003.

Also Tuesday, the U.S. military reported that a car bomb struck a U.S. patrol on the road to Baghdad's airport, wounding four American soldiers and several Iraqis.

The car bomb destroyed an armored Humvee and around 10 civilian vehicles on the highway. Ambulances rushed at least two women -- one of them covered in blood -- a child and three wounded men to a nearby hospital, wire services reported.

The military said one of the wounded Americans was taken to hospital while the other three were treated on the spot.