WASHINGTON — Pentagon leaders scrambled Thursday to contain damage from an Internet video purporting to show four Marines urinating on Taliban corpses — an act that appears to violate international laws of warfare and further strains U.S.-Afghan relations.

Defense Secretary Leon Panetta called Afghan President Hamid Karzai to offer assurances of a full investigation and the top Marine general promised an internal probe as well as a criminal one.

Investigators moved quickly to identify and interview at least two of the four Marines. They were members of a battalion that fought for seven months in former Taliban strongholds in southern Afghanistan.

Their unit, the 3rd Battalion, 2nd Marines, returned from Helmand province to its home base at Camp Lejeune, N.C., last September. Marine officials said that a battalion officer confirmed to investigators on Thursday, based on his examination of the video, that the four men depicted urinating had been members of the battalion. Two have since moved on to other units.

As the video spread across the Internet in postings and re-postings, U.S. officials joined with Afghans in calling it shocking, deplorable, inhumane and a breach of military standards of conduct. It shows men in Marine combat gear standing in a semicircle urinating on the bodies of three men in standard Afghan clothing, one whose chest was covered in blood.

It’s not certain whether the dead were Taliban fighters, civilians or someone else.

The incident will likely further hurt ties with Karzai’s government and complicate negotiations over a strategic partnership arrangement meant to govern the presence of U.S. troops and advisers in Afghanistan after most international combat troops withdraw by the end of 2014.

It also comes 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.

Anti-American sentiment is already on the rise in Afghanistan, especially among Afghans who have not seen improvements to their daily lives despite billions of dollars in international aid. They also have deplored the accidental killing of civilians during NATO airstrikes and argue that foreign troops have culturally offended the Afghan people, mostly when it comes to activities involving women and the Quran, the Muslim holy book.

Pentagon officials said the criminal investigation would likely look into whether the Marines violated laws of war, which include prohibitions against photographing or mishandling bodies and detainees. It also appeared to violate the U.S. Uniform Code of Military Justice, which governs conduct. Thus, some or all of the four Marines could face a military court-martial or other disciplinary action.

Karzai called the video “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.

U.S. officials said a military criminal investigation was being led by the Naval Criminal Investigative Service, the law enforcement arm of the Navy. The Marines will do their own internal investigation.

Panetta said the actions depicted in the brief video 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 chairman of the Joint Chiefs of Staff, Army Gen. Martin Dempsey, said he was deeply disturbed by the video and worried that it would erode the reputation of the entire military, not just the Marine Corps.

A veterans group, the Iraq and Afghanistan Veterans of America, noted the video was the act of a small number of Marines and said it did not reflect the behavior of the millions who have served honorably.

“Our troops and veterans are already facing enormous challenges and stereotypes both overseas and at home, and we encourage the public and media worldwide to refrain from rushing to stereotypes,” the group said in a statement.

Navy Secretary Ray Mabus, the top civilian executive of the Marines and Navy, said it was “appalling and outrageously offensive,” and Marine Commandant James Amos called it “wholly inconsistent with the high standards of conduct and warrior ethos” demanded in the Corps.

White House press secretary Jay Carney said President Barack Obama was aware of the story but may not have seen the video.

Asked how the development might affect U.S.-Afghan-Taliban peace efforts, Secretary of State Hillary Rodham Clinton did not directly reply.

“The United States remains strongly committed to helping build a secure, peaceful, prosperous, democratic future for the people of Afghanistan,” she said. “And we will continue to support efforts that will be Afghan-led and Afghan-owned to pursue the possibility of reconciliation and peace.”

On the streets of Afghanistan, the reaction was cool.

“If these actions continue, people will not like them (the Americans) anymore and there will be uprising against them,” Mohammad Qayum, said while watching a television news story about the video that was airing in a local restaurant in Kabul.

Ahmad Naweed, a shopkeeper in Kandahar, the birthplace of the Taliban insurgency, said, “On the one hand, the Americans present themselves as friends of Afghanistan and … they also try to have peace talks with the Taliban. So we don’t know what kind of political game they are playing in Afghanistan.”

This kind of embarrassment dispersed over the Internet is not new for the Pentagon.

Over the years of combat in Iraq and Afghanistan, officials periodically have been stunned by the troops’ penchant for taking photos or videos of themselves in acts ranging from criminal to simply stupid.

Outrage spread instantly across the globe in 2004 over the release of photos taken by a group of U.S. military police abusing prisoners at the Abu Ghraib prison in Iraq. The troops were grinning and posing beside naked detainees stacked in a pyramid, held on a leash and so on.

In 2008, a Marine was kicked out of the service after being videotaped throwing a puppy off a cliff while on patrol in Iraq and joking about it as the animal yelped.