Grieving relatives and supporters on Monday buried a Syrian filmmaker who was assassinated in Turkey after producing documentaries hostile to the "Islamic State" (ISIS) terrorist group.

Dozens of supporters attended the funeral of Naji Jerf, 37, in the southeastern Turkish city of Gaziantep before he was laid to rest, an AFP photographer said.

Fellow activists from the citizen journalism group Raqa is Being Slaughtered Silently (RBSS) had said Jerf, a father of two, was shot dead in Gaziantep on Sunday with a silencer-equipped pistol.