Kurdish militants attacked a convoy of Turkish troops Sunday near the borders with Iran and Iraq, putting hopes for peace even further out of reach.
Guerrillas from the outlawed Kurdistan Workers Party - the PKK - say they killed 15 solders when they fired on two military vehicles in Hakkari province.
The death toll has not been independently confirmed.
Turkey's Prime Minister Ahmet Davutoglu hurried back to Ankara from the city of Konya for an emergency meeting with his security team. President Recep Tayyip Erdogan said in a television interview that "a new strategy will be adopted in the fight against (PKK) terror. We'll continue with determination."
Sunday's attack by the Kurds may be the deadliest since July, when violence by both sides wrecked a 2-year-old cease-fire.
The Kurds have been fighting a 30-year guerrilla war for more Kurdish autonomy in southern Turkey and northern Iraq.
Turkey, the European Union and United States regard the PKK as a terrorist group.