Fighting erupted late Sunday during a security operation against the outlawed Kurdistan Workers' Party (PKK) on Mount Cudi in Sirnak province, the source said.

The PKK, which is listed as a terrorist group by Turkey and several Western countries, has been fighting for self-rule in Turkey's Kurdish-populated east and southeast since 1984. The conflict has claimed more than 37,000 lives.

Turkey has stepped up military action against the group since December, carrying out air strikes plus a week-long ground incursion into northern Iraq, where it says more than 2,000 PKK rebels have taken refuge.