A British commando was found guilty Friday of murdering an injured Afghan insurgent by shooting the captured man in the chest.

The Royal Marine, known only as Marine A, was found guilty of murdering the unknown Afghan national in the southern Helmand Province in 2011.

Two others, Marines B and C, were acquitted of the charges against them at the court-martial in Bulford, southwest England.

As the victim convulsed and died in front of him, Marine A quoted a William Shakespeare phrase.

"There you are. Shuffle off this mortal coil, you xxxx. It's nothing you wouldn't do to us," Marine A told the insurgent after shooting the man in the chest from close range with a nine-millimetre pistol.

He then turned to his comrades and said: "Obviously this doesn't go anywhere, fellas. I just broke the Geneva Convention."

The execution was filmed by a camera on Marine B's helmet.

Marine A was convicted by a seven-strong board, consisting of officers and non-commissioned officers, following a two-week trial.

He faces life imprisonment. He will be sentenced on December 6, when the court will announce the minimum term he will serve.

Marine A had denied murdering the captured man.

Marines B and C were acquitted of having been "party to the killing" and having "encouraged and assisted" their comrade in committing the murder.