WASHINGTON — Defense Secretary Leon Panetta this morning condemned as “utterly deplorable” a video that purports to depict four U.S. Marines urinating on the corpses of Taliban fighters, saying such behavior is “entirely inappropriate for members of the United States military” and those responsible will be held accountable.

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.

The Marine Corps said Wednesday it would investigate the YouTube video but had not yet verified its origin or authenticity.

The video, posted on the Internet, shows men in Marine combat gear, standing in a semicircle over three bodies. It’s not clear whether the dead were Taliban or civilians or someone else.

Panetta said the actions, if true, were inexcusable.

“I have seen the footage, and I find the behavior depicted in it utterly deplorable. I condemn it in the strongest possible terms,” Panetta’s statement said.

“Those found to have engaged in such conduct will be held accountable to the fullest extent.”