The video is titled: "Abu Musab al-Zarqawi shown slaughtering an American."
The title makes it clear that al-Zarqawi, considered a close Al-Qaeda associate by Washington, wants to take full credit for what the camera records.
The videotape shows 26-year-old Nicholas Berg kneeling on the floor as one of the masked men reads a statement saying he will be killed in response to the abuse of Iraqi prisoners at Abu Ghurayb prison.
Next, a man puts a large knife under Berg's neck and begins sawing off his victim's head. The killer shouts "God is Great" over Berg's screams. Then, he holds up the severed head to the camera like an executioner.
The videotape marks the return of al-Zarqawi, a Jordanian militant, to the frontlines of the Iraq crisis -- and in the ruthless way that has become his trademark.
Al-Zarqawi, considered an influential militant leader and organizer, was most recently charged by U.S. officials with masterminding the massacre of Shi'a pilgrims in Karbala and Baghdad on 2 March.
U.S. officials have called those attacks an attempt to foment sectarian war between Iraqi Sunnis and Shi'a. Coalition forces intercepted a letter from al-Zarqawi to Al-Qaeda leaders in Afghanistan urging them to help Iraqi Sunni insurgents expel foreign troops by making Iraq too chaotic to control.
The beheading of Berg, an entrepreneur who was seeking business opportunities connected to Iraq's reconstruction, has outraged the U.S. public.
Many opinion makers have called it an act of barbarism. One U.S. lawmaker, Senator John McCain (Republican, Arizona), put his feelings this way yesterday: "It's terrible; it's tragic; it also shows the stark difference between America and these barbarians. We have found instances of mistreatment of prisoners; we are addressing the issue completely. These people have no regard for humanity or any other common decency, and that's why we've got to win in Iraq, that's why we have to get rid of these kind of individuals so the Iraqi people are never cursed with them again."
In the Arab world, reaction to the killing is mixed. The videotape comes just two weeks after worldwide publication of photos of the Abu Ghurayb abuses caused a regional outpouring of anger against Washington.
Hazem Saghie is a senior political commentator for the London-based Arabic-language newspaper "Al-Hayat." He says that al-Zarqawi has sought to make his execution of Berg a symbol of the anger resulting from the Abu Ghurayb photos. And he says many people might accept it that way, despite the brutality of the act: "The way it is going to be conceived [by many people in Iraq and the region is] that, well, the Americans came here, they did this, they did that, and that Zarqawi and his gang are just reacting to something else which is started by the United States."
If so, the videotape will further fuel what is becoming a rapidly escalating war of images over how the U.S. presence in Iraq is perceived in the region. On one side is Washington's argument that it is investing billions of dollars, and American lives, in transforming the country into a democracy. On the other side are the images from Abu Ghurayb and, now, al-Zarqawi's effort to portray Iraqi anger over it in murderous terms.
How much al-Zarqawi will succeed in his bid remains to be seen. In killing Berg, al-Zarqawi's group has gone far beyond the limits so far observed by most Iraqi hostage takers.
In most cases, foreigners taken in Iraq have been released after their captors used them to underline anticoalition messages.
However, one Italian security contractor was killed in April by a group which sent a videotope of his death -- by gunshot to the head -- to the Qatar-based television station Al-Jazeera. The Arabic satellite channel refused to air the tape, calling it too gruesome to be made public.