US Defense Secretary Leon Panetta expressed outrage on Thursday over a video that appears to show four Marines urinating on the bodies of dead Taliban fighters in Afghanistan.
"I have seen the footage, and I find the behaviour depicted in it utterly deplorable," he said in a statement. "I condemn it in the strongest possible terms. Those found to have engaged in such conduct will be held accountable to the fullest extent."
Panetta said he instructed the Marine Corps leadership and the commander of NATO forces in Afghanistan, Marine Gen. John Allen, to conduct a thorough investigation.
In a telephone call earlier Thursday, the secretary told Afghan president Hamid Karzai "that the conduct depicted in the footage is utterly deplorable, and that it does not reflect the standards or values American troops are sworn to uphold", a Pentagon spokesman said.
The Marine Corps said efforts continued to verify the origins and authenticity of the 39-second video clip.
The Pentagon has strived to avoid this kind of incident in the wake of the outrage sparked in 2004 by the emergence of photos and video showing US personnel torturing and mistreating prisoners at Abu Ghraib prison in Iraq.