Image caption Gibbs' 5th Stryker Brigade was deployed in western Kandahar, Afghanistan

A US military court has convicted an American soldier of three counts of premeditated murder for leading a rogue "kill team" in Afghanistan.

Sgt Calvin Gibbs, 26, admitted cutting and keeping fingers from corpses as war trophies, but said he was returning enemy fire and did not set out to kill.

He was given life for 15 convictions related to the killing of three men, but could be paroled within nine years.

Three co-defendants in the case pleaded guilty, and two testified against him.

Gibbs, from Billings, Montana, was the highest-ranking of the soldiers charged with murder.

Prosecutors told the jury that Gibbs and the other soldiers dropped weapons by the bodies to make them appear to be combatants.

Gibbs' lawyer argued that the three who pleaded guilty conspired to blame him for their own actions.

The jury of five deliberated for four hours before announcing the verdict, pronouncing him guilty on all 15 charges against him.

He faces life in prison.

Unanswered call

The investigation initially began as a wider inquiry into 5th Stryker Brigade, the unit Gibbs deployed with to Afghanistan.

The platoon was "out of control", a prosecutor said, including smoking hash, photographing Afghan remains and beating a soldier who reported the drug use.

One member of the brigade, then-Specialist Adam Winfield, told his parents when the first Afghan civilian was killed, and alerted them more killings were planned.

Media playback is unsupported on your device Media caption Two former colleagues testified to army investigators about the alleged self-styled "kill team"

But nothing appeared to change after Winfield's father called to report the information to a sergeant at the American base where the brigade was based.

Winfield pleaded guilty to involuntary manslaughter in the last killing, and received a reduced sentence.

He testified at a hearing that he believed Gibbs would kill him if he did not take part in the violence.

Testimony also came from Spc Jeremy Morlock, who is serving 24 years in prison for his involvement.

According to Morlock, when Gibbs joined the platoon in 2010, he began describing scenarios to kill civilians, saying it would be easy to get away with.

Morlock testified that Gibbs used grenades against two of his victims, and placed an AK-47 near another victim to make it appear he had been armed.

'Disassociated'

Gibbs took the stand in his own defence during the seven-day court martial, saying he kept the fingers of the dead Afghans because he was "disassociated" during combat and said it was "like keeping the antlers off a deer you'd shoot".

The killings occurred during routine patrols in Afghanistan's Kandahar province in early 2010.

In March 2011, photographs were published showing the soldiers posing with the bloody corpses of Afghan civilians they had just killed.

The images, described by the US Army as "disturbing and in striking contrast to the standards and values of the US Army" prompted the army to apologise for the distress the photos caused.

In addition to the five soldiers charged with murder, seven other soldiers were charged with less serious, related offences.

Most have agreed to plea deals and all but two have been convicted.