Two US army soldiers allegedly involved in a 12-man "kill team" accused of murdering Afghan civilians for sport have been shown in leaked photographs posing with one of their victims.
Specialist Jeremy Morlock and Private Andrew Holmes are shown holding up the head of a man identified by Germany's Der Spiegel newspaper as Gul Mudin, an unarmed Afghan they are accused of killing on January 15, 2010.
The newspaper first released the images behind a pay-wall online on Sunday night and then published them on Monday.
Their release coincides with an anticipated speech on Monday by Hamid Karzai, the Afghan president, that will announce the beginning of a transfer of security from international to Afghan control.
The photos are said to be among a number seized by Army investigators looking into the deaths of three unarmed Afghans last year.
Der Spiegel uncovered around 4,000 photos and videos taken by the so-called kill squad. The images released on Sunday were covered by a judicial order from a military court prohibiting their dissemination, and it was unclear how the newspaper obtained them.
"Today Der Spiegel published photographs depicting actions repugnant to us as human beings and contrary to the standards and values of the United States Army," the army said in a statement released by Colonel Thomas Collins.
"We apologise for the distress these photos cause."
Their publication has sparked fears of a backlash against armed forces in Afghanistan.
Many organisations with foreign staff, including the United Nations, ordered a "lockdown" on Sunday night and told employees to stay in their compounds, anticipating violent protests in response to the release, the Guardian newspaper reported.
Morlock has pleaded guilty to three charges of murder and will be sentenced at a court martial on Wednesday. Holmes has also been charged with Mudin's death.
Three other soldiers are charged with murder, while seven are charged with trying to block the investigation, using a controlled drug and "wrongfully photographing and possessing visual images of human casualties." All 12 men belonged to the 5th Stryker Briagde, 2nd Infantry Division.
Holmes and Morlock were on guard at the edge of a poppy field on one side of a wall when Mudin began to approach from the other side, according to reports.
Another member of the squad, Staff Sergeant Calvin Gibbs, allegedly handed a grenade to Morlock, who then armed and dropped it on the other side of the wall. Holmes opened fire on Mudin, the grenade exploded, and then other soldiers opened fire as well.
Morlock told investigators he and Holmes shot Mudin without cause, but Holmes has said that he fired when Morlock told him to, believing that Morlock had perceived a legitimate threat.
Holmes and his lawyer said the incident occurred in the dark, but the images were shot during the day.
Geoffrey Nathan, a lawyer for Morlock, has also questioned the authenticity of the photographs, saying they do not have a time or date stamp and the identity of the corpse was unverifiable.