BERLIN (AFP) - A Syrian suspected of being among extremists who kidnapped a UN peacekeeper in Damascus in 2013 has been arrested over the "war crime", Germany's federal prosecutor said on Friday (Jan 22).

"Investigations found that the accused was part of the armed group and was involved in guarding the kidnapped victim between March and June 2013," the prosecutor said in a statement.

The peacekeeper, whose nationality was not revealed, managed to free himself in October 2013.