US defence secretary Leon Panetta said he found the marines' behaviour 'utterly deplorable' Reuters

Afghan president Hamid Karzai and US defence secretary Leon Panetta have led a chorus of condemnation of American soldiers filmed urinating on the bodies of dead Afghans as "inhumane" and "utterly deplorable".

The Pentagon said it has identified two of the four marines responsible for the latest in a series of abuses by US forces which is likely to further inflame hostility to Nato troops in Afghanistan and reinforce the perception that there is an institutional problem in the American military.

Panetta said he had viewed the graphic video of four US marines urinating on three bloodied corpses. As they are filmed by a fifth soldier, the marines sigh with relief, laugh and make comments including "have a great day, buddy" and "golden, like a shower".

"I have seen the footage, and I find the behaviour depicted in it utterly deplorable," said Panetta. "Those found to have engaged in such conduct will be held accountable to the fullest extent."

The soldiers in the undated video, which was posted anonymously on the web, appear to be members of Scout Sniper Team 4, a US marine unit based in North Carolina that served in Afghanistan until last autumn. The military said it knows the names of two of those in the video and that they are no longer serving with the unit, but it declined to make their identities public.

It is not clear who the dead Afghans are. They are possibly Taliban fighters but their corpses are not shown with weapons.

Karzai said in a statement that he was "deeply disturbed" by the desecration of dead bodies which is defined as a war crime by the Geneva conventions.

"This act by American soldiers is completely inhumane and condemnable in the strongest possible terms. We expressly ask the US government to urgently investigate the video and apply the most severe punishment to anyone found guilty in this crime," he said.

The Nato-led International Security Assistance Force (Isaf) said it "strongly condemns the actions depicted in the video, which appear to have been conducted by a small group of US individuals, who apparently are no longer serving in Afghanistan".

"This disrespectful act is inexplicable and not in keeping with the high moral standards we expect of coalition forces," it said.

John McCain, a navy veteran and the leading Republican on the US senate's armed services committee, said the video "makes me so sad".

"There should be an investigation and these young people should be punished," he said.

A leading negotiator in Karzai's peace council, Arsala Rahmani, said that the film will have a "very, very bad impact on peace efforts".

"Looking at such action, the Taliban can easily recruit young people and tell them that their country has been attacked by Christians and Jews and they must defend it," he said.

But the Taliban, while criticising the actions of the marines as "shameful", said the latest revelations of abuse by US forces will not block attempts to get talks started to bring an end to the Afghan conflict.

A Taliban spokesman, Qari Yousuf Ahmadi, told the BBC that it is not the first time Americans had carried out such a "wild action". But another different Taliban spokesman, Zabihullah Mujahid, said the video "is not a political process, so the video will not harm our talks and prisoner exchange because they are at the preliminary stage".

The exposure of the video, widely viewed on the web, comes as the Obama administration attempts to begin peace talks with the Taliban before the US begins to withdraw its forces from Afghanistan.

Marc Grossman, the White House special representative, will meet Karzai in Kabul this weekend as well as officials in Turkey, Saudi Arabia and the United Arab Emirates.

Last week, the Taliban announced it would to set up a political office in Qatar which appears to be an important step toward negotiations. Washington is considering reciprocating by releasing several Taliban prisoners from the Guantanamo jail as a confidence-building measure.

While the latest revelation of abuses does not appear likely to derail the latest peace effort it again raises questions about whether there is a culture of abuse in US forces serving in Afghanistan and Iraq.

Last year, 11 soldiers were convicted over the murders of three Afghan civilians by a "kill squad" and the subsequent cover up. It was revealed that some of them collected body parts, including fingers and skull parts, as trophies, and posed for photographs over the corpses of their victims.

This week, a US marine went on trial over the killing of 24 Iraqis, including women and children, in their homes. Staff Sergeant Frank Wuterich faces charges of manslaughter over the killings as he commanded a group of soldiers who burst into the victims' homes in Haditha in search of combatants. Seven other soldiers also charged were either acquitted or had the case against them dropped.

The US military is also still grappling with the legacy of the abuse of prisoners at Abu Ghraib prison in Iraq, and its role in the torture of alleged terrorists.