Fighting erupted during a security sweep late Wednesday against the outlawed Kurdistan Workers' Party (PKK) in a mountainous region in Sirnak province, which borders Iraq and Syria, the sources said.

The PKK, which has bases in the autonomous north of Iraq, has stepped up its military activity this year.

The group has been fighting for self-rule in Turkey's mainly Kurdish areas in the east and southeast since 1984. The conflict that has claimed more than 37,000 lives.

The PKK is considered a terrorist organization by Ankara, the United States and the European Union.