U.S. Defence Secretary Leon Panetta is joining others in his condemnation of a video that appears to show four U.S. Marines urinating on the corpses of Taliban fighters, calling it "utterly despicable."

In a statement released by the Pentagon, Panetta says he has ordered the Marine Corps and a military command office to "immediately and fully investigate the incident.

Panetta said the incident "does not reflect the standards or values our armed forces are sworn to uphold."

The secretary vows that "those found to have engaged in such conduct will be held accountable to the fullest extent."

As outrage spread Thursday, The Associated Press reported that two of the four involved in the video had been identified by Pentagon investigators.

The four were members of the 3rd Battalion, 2nd Marines, which is based in North Carolina. According to the AP report, "at least some of the four Marines are no longer in that battalion."

The 39-second video surfaced on YouTube and other websites on Wednesday and appears to show four men dressed in U.S. Marine uniforms urinating on three lifeless and bloodied bodies of Taliban fighters. Some of the men can be heard chuckling, while one says, "Have a great day, buddy."

Afghan President Hamid Karzai released a statement describing the act as "completely inhumane" and calling for the U.S. military to punish those involved.

And the NATO-led security force in Afghanistan has also condemned the video. In a statement that essentially confirms the video is authentic, the International Security Assistance Force said the actions "appear to have been conducted by a small group of U.S. individuals, who apparently are no longer serving in Afghanistan."

The group added the actions in the video were "inexplicable and not in keeping with the high moral standards" expected of coalition forces.

It wasn't immediately clear who shot the video or why it became public this week.

The case has been referred to the Naval Criminal Investigative Service, the Navy's worldwide law enforcement organization, said NCIS spokesman Ed Buice.

The fear now is that video could spark retaliation against American troops in Afghanistan and outrage across the Muslim world.

In Afghanistan, news of a Qur'an burning by a fringe American pastor prompted deadly riots.

Currently, the American administration is likely most concerned about the impact the video will have on what seems to be a positive beginning to reconciliation in Afghanistan: a move toward peace talks.

In fact, the White House had been prepping for more diplomacy, with special representative Marc Grossman heading to Afghanistan for high-level talks.

Grossman, who is Obama's point-man on Afghanistan and Pakistan, is planning to seal a plan that would allow the Taliban to set up a political office in Qatar.

"They're sending an envoy to the region next week to push this idea of getting down to talks with the Taliban. They're discussing prisoner exchanges and things like that. The worry is what effect does the video have on that kind of movement," said CTV's Paul Workman.

But a Taliban spokesman said although the images were shocking, the tape would not affect plans for those talks.

"This is not the first time we see such brutality," said spokesman Zabihullah Mujahid.

"We know that our country is occupied ... This is not a political process, so the video will not harm our talks and prisoner exchange because they are at the preliminary stage."

U.S. officials, who plan to withdraw combat troops by 2014, have also been planning to move forward with measures that could hand the Taliban a share of governance in Afghanistan.

The initiative would also include the return of Taliban prisoners currently being held at Guantanamo Bay, Cuba.