The Islamic State killed former world champion kickboxer Valdet Gashi for attempting to flee from Syria, sources reported.
The Albanian-born German Muay Thai fighter left his family to join IS in January this year.
The Syrian Observatory for Human Rights reported Gashi was shocked by the IS after he moved to Syria and tried to run away with another group.
He was then arrested and executed.
Gashi’s brother also confirmed his borther’s death on Facebook, according to a Swiss TV channel.
But the Human Rights group also reported other sources claimed that Gashi might still be alive, and planning another escape.
A U.N. report issued in May said that some 20-22,000 foreign fighters are active in the Syria-Iraq conflict zone alone.