Deryan Aktert, who headed the party's branch in Diyarbakir's Dicle district, was attacked in his office at 10:30 pm (1930 GMT) by suspected members of the Kurdistan Workers Party (PKK), the provincial governor's office said.
There was no immediate claim of responsibility, though the PKK - in a mounting conflict with government forces in the region bordering Iran, Iraq and Syria - often waits several days before making such announcements.