WASHINGTON – Defense Secretary Leon Panetta has promised Afghanistan President Hamid Karzai a full investigation of a video that purports to depict four U.S. Marines urinating on the corpses of Taliban fighters – a video both men condemned Thursday as deplorable.

In a separate public statement, Panetta said such behavior is “entirely inappropriate for members of the United States military” and that those responsible will be held accountable.

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

The title on the posting called them Taliban insurgents and said the men were from Camp Lejeune, N.C., but officials would not immediately confirm that.

Officials said they had not yet verified the video’s origin or authenticity, but had no evidence to cast doubt on it.

“It certainly appears to us to be what it appears to be to you guys – troops urinating on corpses,” Pentagon spokesman Capt. John Kirby told reporters Thursday.

The video was roundly denounced in the U.S. and Afghanistan alike.

Karzai called it “completely inhumane.” The Afghan Defense Ministry called it “shocking.” And the Taliban issued a statement accusing U.S. forces of committing numerous “indignities” against the Afghan people.

“First they killed the Afghans with mortars, and they then urinated on their bodies,” Taliban spokesman Zabiullah Mujahid said of what is shown in the video. “We strongly condemn this inhumane action by the wild American soldiers.”

Secretary of State Hillary Rodham Clinton expressed “total dismay” at the video and said it was “absolutely inconsistent with the standards of behavior that the vast majority of Marines hold themselves to.”

Panetta said the actions, if confirmed, 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.”

The video came to light at a delicate time in relations among the United States, Afghanistan’s elected government and the Taliban insurgency fighting for both territorial control and cultural and religious preeminence in Afghanistan.

The U.S. is trying to foster peace talks between the Karzai government and the Pakistan-based Taliban high command, and has made unprecedented offers to build trust with the insurgents, including the planned opening of a Taliban political office to oversee talks.

One of the largest obstacles to peace discussions has been widespread Afghan contempt for U.S. military tactics.

Opposition to the U.S. and NATO military presence in Afghanistan usually centers on civilian casualties from military engagement, although the vast majority of those deaths are caused by the insurgents. The video is likely to resonate with those opposed to the U.S. presence and to peace with the U.S.-backed Karzai government.

U.S. officials seemed to have ordered a variety of investigations:

• 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.
• In a statement, the commandant of the Marine Corps, Gen. James Amos, said he requested on Wednesday evening that the Naval Criminal Investigative Service investigate, and that the Marines would, separately, do their own internal investigation.

“The Marine Corps will not rest until the allegations and the events surrounding them have been resolved. We remain fully committed to upholding the Geneva Convention, the Laws of War, and our own core values,” Amos said.

The NATO-led security force in Afghanistan released a statement Thursday saying, “This disrespectful act is inexplicable and not in keeping with the high moral standards we expect of coalition forces.”

The actions “appear to have been conducted by a small group of U.S. individuals, who apparently are no longer serving in Afghanistan,” the International Security Assistance Force said.

The statement did not identify the personnel or explain why the ISAF thought they had left the country.

A spokesman at Camp Lejeune in North Carolina would not confirm that the Marines were from a unit based there.

“We have had elements of that unit that have deployed to Afghanistan and have returned. However, we have not yet confirmed if anyone in the video is from that unit, or whether they are attached to a unit from Lejeune,” said Capt. Scott Sasser.

Pentagon officials said the criminal investigation would likely look into whether the Marines violated laws of war, which include prohibitions against photographing bodies and detainees and a range of other rules.

Mujahid urged the U.N. and other international groups to end such actions by U.S. troops.

On Wednesday, the Council on Islamic-American Relations, a prominent Muslim civil rights and advocacy group based in Washington, protested the video in a letter to Panetta.

“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,” the group wrote.

“If verified as authentic, the video shows behavior that is totally unbecoming of American military personnel and that could ultimately endanger other soldiers and civilians,” the letter said.

Associated Press writers Slobodan Lekic and Deb Reichmann in Kabul, Afghanistan; Anne Gearan in Washington; and Susanne Schafer in Columbia, S.C., contributed to this report.