It's an old world vulture from the Gyps genius aka Griffon Vultures (they are big and ancient, now extinct), Gyps melitensis or Gyps bochenskii . Or possibly a Sarcogyps calvus or Torgos tracheliotos.
Field papers:
http://www.acta-zoologica-bulgarica.eu/downloads/acta-zoologica-bulgarica/2010/62-2-211-242.pdf