BAGHDAD, Iraq - Kidnappers beheaded British hostage Kenneth Bigley after twice releasing videos in which he wept and pleaded with Prime Minister Tony Blair for his life. A U.S. official said Friday there was credible information that Bigley had tried to escape with the aid of one of his captors.

The attempt failed and Bigley was killed a short time later as was shown on a video of his beheading, the Washington official said on condition of anonymity. There was no word on the fate of his captor. A Western official in Baghdad refused to talk about the escape attempt report.

The 62-year-old civil engineer was the first British hostage killed in Iraq and the 28th overall. He was kidnapped three weeks ago, along with two American co-workers. They were beheaded earlier, and grisly footage of their killings was posted on the Internet.

A videotape sent to Abu Dhabi TV showed Bigley kneeling in front of six masked gunmen, according to a witness who saw the footage. One militant, speaking in Arabic, declared the Briton would be slain because his government refused to release women prisoners detained in Iraq.

The speaker then pulled a knife from his belt and severed Bigley's head as three others pinned him down, said the witness, who spoke on condition he not be identified. The tape ended with the killer holding up the severed head.

Bigley was seized at his Baghdad home Sept. 16 by the most feared terrorist group in Iraq, Tawhid and Jihad, along with Americans Eugene Armstrong, 52, and Jack Hensley, 48. The Americans were beheaded days later.

Abu Dhabi TV did not broadcast the videotape of Bigley, saying it refused "to serve as a mouthpiece for such groups or their actions."

U.S. and British officials in Iraq declined to confirm Bigley's death, saying his body had not been found. However, Bigley's brother, Phil, said the family had received "absolute proof" of his death.

British Foreign Secretary Jack Straw said Friday that messages were exchanged with Bigley's kidnappers through an intermediary in Iraq. But he said the militants refused to drop their demands, "even though they were fully aware there are no women prisoners in our custody in Iraq."