At least 13 fighters of the Kurdistan Workers Party (PKK) have been killed by Turkey's military using helicopter gunships, the office of a regional governor has said.
Wednesday's attack took place in the Amanos mountains at the western end of Turkey's border with Syria, far from the main arena of conflict between Turkish government forces and PKK fighters, the Osmaniye provincial governor's office said.
Troops captured five PKK fighters, the office said, and the operation was continuing.
Turkey has attributed the escalation of violence since the summer to the fighting in neighbouring Syria and has accused
Bashar al-Assad, the president, of resuming support for the PKK and arming its fighters.
The latest Turkish military operation, which began on Monday, was based on intelligence received from a drone indicating PKK fighters were in the area.
Clashes between the army and the fighters generally surge during the summer when snow melts in the mountainous region, with PKK fighters having spent the harsh winter in camps along Turkey's southeast border.
The PKK, labelled as a terrorist organisation by Turkey and much of the international community, began fighting in 1984 with the aim of carving out a separate state in mainly Kurdish southeast Turkey. They now seek autonomy in the region.
The conflict has claimed more than 40,000 lives.