The US military is investigating an online video depicting what appears to be four Marines urinating on the bloodied corpses of Taliban fighters in Afghanistan.
The uniformed men appear to be aware they are being filmed, with one of them making a lewd joke.
Another says: “Have a great day, buddy”, as he relieves himself.
The authenticity of the video has not yet been verified but Pentagon spokesman John Kirby told AFP: “Regardless of the circumstances or who is in the video, this is egregious, disgusting behaviour, unacceptable for anyone in uniform.
“It turned my stomach.”
If verified, the clip is certain to create a strong backlash in the Muslim world and could set back peace talks.
A caption posted with the video claimed the men were members of a scout sniper team from the Third Battalion of the Second Marine Regiment, based in Camp Lejeune, North Carolina.
Arsala Rahmani, the top negotiator from Afghanistan President Hamid Karzai’s High Peace Council, said: “Such action will leave 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.”
Muslim civil rights and advocacy group, the Council on Islamic-American Relations, condemned the footage in a letter to US Defence Secretary Leon Panetta.
It said: “We condemn this apparent desecration of the dead as a violation of our nation’s military regulations and of international laws of war prohibiting such disgusting and immoral actions.
“If verified as authentic, the video shows behaviour that is totally unbecoming of American military personnel and that could ultimately endanger other soldiers and civilians.”
Images of US troops torturing Iraqis at the notorious Abu Ghraib prison led to a surge in violence in 2004.