Paris's special assizes court found the Montpellier native guilty of murders committed as part of an organized criminal group during a double public execution in 2015 in Syria, as well as terrorist criminal association.
Three successive attacks on Malian army positions demonstrate the growing power of the Al-Qaeda-affiliated jihadist group.
Tried by Paris's special assize court for beheadings committed in Syria, this 32-year-old from Montpellier claimed Friday to have discovered "a different vision of life" in prison, while facing a possible life sentence.
The GSIM, affiliated with Al-Qaeda, claimed responsibility for the attack on a military base at Dioura on September 10.