Panetta said he had ordered the Marine Corps and Marine Gen. John Allen, the top commander of the NATO-led forces in Afghanistan, to fully investigate.
Marines urinating on dead soldiers Taliban
The Marine Corps said Wednesday it would investigate the YouTube video but had not yet verified its origin or authenticity. The case has been referred to the Naval Criminal Investigative Service, the Navy's worldwide law enforcement arm.
The video, posted on the Internet, shows men in Marine combat gear, standing in a semi-circle over three bodies. It is not clear whether the dead were Taliban or civilians or someone else. The title on the posting called them Taliban insurgents but it was unclear who added that title, Marine Corps officials in Washington said.