http://news.bbc.co.uk/2/hi/middle_east/3705409.stmVideo 'shows US man beheaded'
The victim said he was an American from Philadelphia
An Islamic militant website has shown a video purporting to show the beheading of an American in Iraq.
The video showed five men in headscarves and ski masks cutting off the man's head with a knife.
Moments earlier the victim, bound and dressed in an orange jumpsuit, said he was an American from Philadelphia.
The group, thought to be linked to al-Qaeda, said it was carrying out the killing in retaliation for the abuse of Iraqi prisoners by US soldiers.
The poor-quality tape - shown on the Muntada al-Ansar site - began with the victim sitting on the floor with five masked men behind him.
It was titled "Abu Musab al-Zarqawi shown slaughtering an American".
However, it was not clear whether al-Zarqawi - a senior al-Qaeda operative accused of masterminding multiple bomb attacks against US forces in Iraq - was actually in the video.
'Devilish scorn'
The victim identified himself as Nick Berg, a US civilian who was said to have been working on repairing Iraq's infrastructure. His body was found near a highway overpass in Baghdad on Saturday.
You will not receive anything from us but coffins after coffins slaughtered in this way
Voice on tape
"My father's name is Michael, my mother's name is Suzanne," the man said on the video. "I have a brother and sister, David and Sarah. I live in... Philadelphia."
One of the masked men read out a statement, saying they had offered to exchange the man for inmates of Abu Ghraib prison but the coalition authorities refused.
"How can a free Muslim sleep well as he sees Islam slaughtered and its dignity bleeding, and the pictures of shame and the news of the devilish scorn of the people of Islam - men and women - in the prison of Abu Ghraib?" he said.
"You will not receive anything from us but coffins after coffins... slaughtered in this way."
The statement also threatened US President George W Bush, saying he would regret the day he stepped into Iraq.
It described Pakistani President Pervez Musharraf as a "traitor agent".
Disappearance
After reading the statement, they pulled the man to the side and put a knife to his neck.
The man screamed as he was killed.
His killers shouted "Allah is great" before holding what appeared to be a head up to the camera.
The 26-year-old Mr Berg, who owned a communications equipment company, was involved in rebuilding antennas in Iraq before he disappeared on 9 April.
