A posting on an Islamic Internet site Saturday claimed that an Al Qaeda-linked (search) group has killed British hostage Kenneth Bigley (search). The claim could not immediately be confirmed.

Bigley was kidnapped Sept. 16 with two Americans, Eugene Armstrong and Jack Hensley, who have since been beheaded. They were all taken — from their home in Baghdad — by the Tawhid and Jihad group of Jordanian terror mastermind Abu Musab al-Zarqawi (search).

The Web site where the posting appeared has often carried messages from Zarqawi's followers, including gruesome video that showed Hensley and Armstrong being killed. It also showed video on Wednesday of Bigley, 62, begging for his life.

The Foreign Office in London said it was aware of the claim but described the site as "discredited."

"We don't think it's anything to be taken too seriously," the Foreign Office statement said.

Saturday's message also claimed that seven British troops had been captured, but Capt. Donald Francis, a spokesman for the British military said that all forces "are accounted for."

He had no information on the claim to have executed the British hostage.

The statement appeared in red script on the Web site and consisted of only two sentences: "Tawhid and Jihad announces that it has executed the British citizen and gives you the good news of kidnapping seven British soldiers. We will be releasing the tape shortly."

In the video released Wednesday, Bigley was shown begging authorities to meet his kidnappers' demands to free all female Iraqi prisoners and save his life. The United States says there are two high-profile women in custody in Iraq and there are no plans to release them.

The posting came a day after Bigley's 86-year-old mother Lil begged the kidnappers to let her son go free.

"Please show mercy to my Ken and send him home to me alive," she said in a video statement, sitting behind a table between two of her other sons and grasping one's hand. "His family need him. I need him."

Hours after making the statement, Lil Bigley was taken to a local hospital, where officials said her condition was stable. It was not clear what she was being treated for.

Bigley's wife, Sombat, also pleaded with the militants to release him.

"We have been married for seven years and I love him very much," she said from her home in Thailand. "I desperately want to be reunited with my husband. I plea for your mercy now, and beg that you release Ken so that I may be with him again."

Flyers from Bigley's family had also been distributed around Baghdad pleading for his release.

More than 140 foreigners have been kidnapped in Iraq — some by anti-U.S. insurgents and some by criminals seeking ransoms. At least 26 of them have been killed.