ISTANBUL, Turkey (AP) — Six Turkish soldiers were killed Saturday in clashes with Kurdish militants in northern Iraq, a day after another six were also killed.

The six soldiers slain on Saturday died in a firefight when militants attempted to infiltrate a Turkish base, according to a statement by the Turkish Defense Ministry. The statement said 13 militants had been “neutralized.”

In addition to the six Turkish soldiers killed on Friday, four militants were slain, authorities said.

Turkey conducts operations and airstrikes against targets in Syria and Iraq that it believes to be affiliated with the Kurdistan Workers’ Party, or PKK, a banned Kurdish separatist group that has waged an insurgency against Turkey since the 1980s.

Ankara maintains that PKK has sanctuaries in northern Iraq, where its leadership is also purportedly based. The PKK is considered a terror organization by the United States and the European Union. Tens of thousands of people have died since the start of the conflict in 1984.