The White House and NATO on Wednesday condemned grisly photographs showing US soldiers with the mangled remains of suspected Taliban suicide bombers in Afghanistan.
White House spokesman Jay Carney said the photos were "reprehensible" but also said the administration was "very disappointed" that the Los Angeles Times decided to publish them.
The incident is the latest in a series of scandals that have strained US-Afghan ties and cast NATO-led troops in a negative light.
Pentagon officials insisted the episode did not signal a wider problem with discipline among US troops, stressing that the incident occurred two years ago.
NATO chief Anders Fogh Rasmussen also denounced the photos but said it did not represent the values of the alliance's military mission.
"These events took place apparently a couple of years ago and I consider them an isolated event," he said in Brussels during a NATO meeting.
US Defense Secretary Panetta, who was in Brussels for the alliance talks, said through a spokesman that the photos do not reflect the "values or professionalism" of America's fighting forces in Afghanistan.
"Secretary Panetta strongly rejects the conduct depicted in these two-year-old photographs," Pentagon spokesman George Little said in a statement.
"These images by no means represent the values or professionalism of the vast majority of US troops serving in Afghanistan today," he said, adding that the Pentagon has opened an investigation that could lead to disciplinary measures.
He also expressed the US defense chief's disappointment that the LA Times ignored a Pentagon request to refrain from publishing the pictures, which reportedly were obtained from a soldier in the division.
"The danger is that this material could be used by the enemy to incite violence against US and Afghan service members in Afghanistan. US forces in the country are taking security measures to guard against it," the spokesman said.
General John Allen, commander of NATO-led forces in Afghanistan, also condemned the photos.
The unsettling images, which appear on the Times' website, showed troops posing in one image with a severed hand and in another with disembodied legs. They are the latest in a series of scandals that has strained US-Afghan ties.
The Times reported that the images were taken during more than one occasion over the course of 2010.
The first incident took place in February 2010, when paratroopers from the 82nd Airborne Division were sent to an Afghan police station in Zabul province to inspect the remains of an alleged suicide bomber.
The soldiers had intended to try to get fingerprints and possibly scan the irises of the corpse, but instead they posed for pictures next to the Afghan police, holding up or squatting beside the remains, the newspaper said.
A few months later, the same platoon went to inspect the remains of three insurgents whom Afghan police said had blown themselves up by accident.
Two soldiers posed holding up one of the dead men's hands with the middle finger raised, while another leaned over the bearded corpse, the newspaper reported.
Another soldier apparently placed an unofficial platoon patch reading "Zombie Hunter" next to the other remains and took a picture.
LA Times editor Davan Maharaj said that the newspaper decided to publish a "small but representative selection" of the images because of their news value and to "fulfill our obligation to readers to report vigorously and impartially on all aspects of the American mission in Afghanistan."
The episode seemed likely to test already frayed US-Afghan relations, after a series of incidents in which US troops have been accused of misconduct.
The release in January of video clips online showing American marines urinating on the bodies of Afghan combatants sparked outrage in Kabul.
That was followed by the inadvertent burning of Korans by US soldiers in mid-February, which triggered deadly anti-US protests and may have motivated a surge of "insider" attacks on NATO troops by Afghan forces.
In March, a US soldier allegedly went on a shooting rampage in two Afghan villages, killing 17 people -- mostly women and children -- in what is believed to be the deadliest war crime by a NATO soldier in the decade-long conflict.
NATO has a 130,000-strong US-led military force fighting the Islamist Taliban, which has led an insurgency against the Western-backed Kabul government since being toppled from power in 2001.
