A videotape shows British hostage Kenneth Bigley (search) being beheaded by his captors in Iraq, a witness who saw the tape said Friday.

The witness, who asked not to be identified by name, said the tape shows six hooded, armed men standing behind the kneeling Bigley, whom the witness recognized from two previous tapes released by the kidnappers.

One of the six then spoke in Arabic for about a minute. Afterward, the speaker took a knife from his belt and severed Bigley's head as three others held him down, the witness said. The tape ends with the killer holding up the severed head.

British officials in Baghdad said they had no confirmation that Bigley was dead, and American military authorities said no body had been found.

Bigley, 62, was abducted along with two Americans from their home in the upscale Mansour neighborhood by members of Tawhid and Jihad (search), Iraq's most feared terrorist group led by Abu Musab al-Zarqawi (search), who demanded the release of all female prisoners held by the coalition in Iraq.

The two Americans — Eugene Armstrong (search), 52, and Jack Hensley (search), 48 — were decapitated a few days later.

Two videos have surfaced showing Bigley pleading with British Prime Minister Tony Blair (search) to save his life by meeting his kidnapper's demands.

On Wednesday, British Foreign Secretary Jack Straw said his government was ready to listen to the kidnappers but would not enter into negotiations with them for the hostage's release.