IRAQI kidnappers beheaded an American on video last night - but said two more Western hostages, including Briton Kenneth Bigley, would have the deadline for their executions delayed by 24 hours.

The announcement was made as a video was released on a website showing the beheading of Eugene Armstrong.

In the video, five black-clothed men stand behind the figure of a sobbing man. One reads out a statement, then appears to pull a knife, rushes to the blindfolded hostage from behind and cuts his throat.

The hostage-takers are demanding the release of Iraqi women from prisons.

Last night, Mr Bigley's son, Craig, 33, made an anguished plea to Prime Minister Tony Blair.

He said: ''Please meet the demands and release my father - two women for two men.''

Earlier, in the kidnappers' film, the speaker said: "The fate of the first infidel was cutting off the head before your eyes and ears.

"You have a 24-hour opportunity.

"Abide by our demand in full and release all the Muslim women, otherwise the head of the other will follow this one."

He appeared to indicate the hostages would be killed one at a time and did not specify whether Mr Hensley or Mr Bigley would be next.

The US State Department confirmed a body had been recovered, and efforts were being made to identify it. But a US official said the body was Mr Armstrong's.

Abu Musab al-Zarqawi's group Tawhid and Jihad has demanded that women, allegedly held by coalition authorities in the Abu Ghraib and Umm Qasr prisons, be let out.

The US military says no women are held at either facility, although it says two female "security prisoners" are held elsewhere.

Alleged al Qaida supporter al-Zarqawi's organisation is the group that claimed it beheaded American Nicholas Berg.

Al-Zarqawi has been named as the link between Iraq and Osama bin Laden's terror network, and is accused of orchestrating suicide bombings and attacks in the Middle East country.

A Foreign Office spokesman said last night: "The British Government utterly condemns the kidnapping and murder of all innocent civilians.

"This appalling crime strengthens our resolve to work with the Iraqi Government and people to bring security, stability and democracy to Iraq."

Earlier yesterday, Mr Blair remained silent about the Government's efforts to secure Mr Bigley's release.

Asked for an update on the case, he said: "I don't think it is sensible for us to say anything at all at the present time except to say, obviously, that we are focused on doing what we can."