Two Turkish soldiers also died during the air and land operations against PKK targets in Hakkari province.
The Turkish military said on Thursday that 21 militants were killed in an area close to the Iraqi border during land and air operations against PKK targets.
The PKK, listed as a terrorist organisation by Turkey, the US, and EU, has relaunched its decades-old armed campaign in the country in July of last year. Over 700 security force members have been killed during the conflict so far, while around 8,000 terrorists were killed or apprehended.
In a statement, Turkish General Staff said two Turkish soldiers were also killed and five wounded during the air and land operations in Cukurca, a mountainous district in the southeastern province of Hakkari.
The injured soldiers were rushed to the hospitals in the region.
The statement said the fighting focused on two areas - Uzundere Hisar and Guven - between midnight and early morning.
Nine terrorists were killed by grounds troops, while two others were killed by an armed aerial drone. The remaining 10 were hit by Turkish Air Force jets.
Meanwhile, two PKK terrorists were killed during a security operation in Dogubeyazit, close to the Iranian border, the local governor's office said.
In a statement, the governorate of Agri province said security forces seized two rifles, eight grenades and ammunition during a raid.