Corporal Jeremy Morlock has confessed to three murders. In January 2010 he threw a grenade at a boy before opening fire along with other members of his squad. He has also admitted to murders in February and May 2010.

On each occasion the crime was carefully planned, covered up and photographs taken. Morlock is said to have distributed the trophy photographs freely and widely.

Under a plea bargain which is yet to be approved by a judge, Morlock would receive a 24-year prison sentence in return for testifying against other members of a so-called “kill team” in a court martial being held at the Joint Base Lewis-McChord in Washington state.

Besides Morlock, four others are accused of premeditated murder and face the death penalty or a life sentence if found guilty. Seven other soldiers are charged with helping to cover up the offenses.

Photographs of the soldiers – including Morlock – posing with the dead bodies of the civilians they allegedly murdered were published in the German magazine Der Spiegel on Sunday and are now widely available on the internet.

The magazine quotes a Facebook chat between one of the accused, 21-year-old Adam Winfield, and his father. Winfield describes the January 2010 incident, saying: “They made it look like the guy threw a grenade at them and mowed him down.”

The publication of the photographs, which had been prevented in the United States by a court order, prompted the US Army to release a statement apologizing for the behaviour of the team, which it described as “repugnant to us as human beings and contrary to the standards and values of the United States Army”.

It is feared the photographs will cause a wave of angry protests in Afghanistan as they become more widely distributed over the internet – and possibly provoke attacks on NATO forces.