Soldiers who were on an operation in Cukurca in Hakkari province bordering Iraq and Iraq returned the fire, sources said. Operations were under way to hunt down the militants.
Turkey's largely Kurdish southeast has been rocked by violence following the collapse of a 2-1/2-year ceasefire between the state and the PKK last year.
The autonomy-seeking PKK took up arms in 1984, and more than 40,000 people have died in the conflict. It is considered a terrorist group by Turkey, the United States and the European Union.