Eight members of Turkey's security forces and five Kurdish militants were killed in a clash early on Thursday near the border between northern Iraq and southeast Turkey, security and hospital sources said.
They said Turkish forces launched a helicopter-backed operation in search of further Kurdistan Workers Party (PKK) militants, who sought to cross the border into Hakkari province's mountainous Semdinli district.
Six Turkish soldiers and two members of the country's state-backed village guard militia were killed in the fighting, along with five PKK members, the sources said.
They said the clashes were continuing.
The PKK launched a separatist insurgency in 1984 and more than 40,000 people have been killed in the conflict. It is designated a terrorist group by Turkey, the United States and European Union.