BERLIN (AFP) - German prosecutors on Thursday (Jan 18) filed a war crime charge against an Afghan Taleban suspect who allegedly killed a policeman by savagely beating him in the head and later shooting him.

The 20-year-old suspect, named as Omaid N, is also charged with one count of murder over the killing, prosecutors said in a statement.

The man is believed to have joined the Taleban in early 2013 and had helped transport weapons for the militant group on at least one occasion.

Together with other members of his Taleban unit, he allegedly beat a captured policeman on the head using wooden slats, prosecutors said, adding that the suspect also fired a shot at the captive.

"The policeman died either from the beating with the wooden slats or later from the shots," said prosecutors.

The suspect was subsequently due to carry out suicide attacks along with other members of the group.

"But he was not ready for that, and fled," said prosecutors, adding that he managed to reach Germany in November 2013 with the help of smugglers.

He was arrested on May 19, 2017, and is now in detention pending trial.

German federal prosecutors have opened over a dozen investigations concerning alleged war crimes in Syria or Iraq, alongside dozens of cases of suspected membership in Islamist militant groups.

The probes have gained momentum with the arrival of more than one million asylum seekers since 2015, including hundreds of thousands from Syria and Iraq, some of whom who helped to provide valuable leads to investigators.

In July 2016, in the first such conviction, a German terrorist was sentenced to two years in prison on war crimes charges after posing for pictures in Syria with the severed and impaled heads of two government soldiers.