Footage on an Islamist Web site has been released, showing an American hostage in Iraq being killed by his captors.
In the pictures the man, identified as Eugene Armstrong, is beheaded.
His body was found tonight in Baghdad.
He was seized in the city last Thursday with another American and a Briton, and the killing was claimed by the militant group of Abu Musab al-Zarqawi, an ally of al-Qaeda.
His captors said they had killed Mr Armstrong because the US authorities had failed to free women prisoners in Iraqi jails within the 48-hour deadline they had set on Saturday.
They gave another 24 hours for the United States to do so, or Jack Hensley and Briton Kenneth Bigley would be killed.
Meanwhile, the Iraqi Prime Minister, Iyad Allawi, has vowed he will not let the spiralling bloodshed upset plans for January elections.
Mr Allawi was speaking as he met his British counterpart, Tony Blair, in London today.
In an interview with an Arabic newspaper published today, Mr Allawi revealed that he himself had escaped four attempts on his life since his government took over from the US-led occupation on 28 June, the last one just five days ago.
