Ten members of Turkey's security forces have been killed in an attack by Kurdish rebels close to the border with Iraq and Syria, officials say.
Around 20 militants also died in the south-eastern province of Sirnak, governor Vahdettin Ozkan said.
The fighting broke out late on Sunday evening and was continuing, he said.
Clashes between the army and the rebel PKK - which seeks autonomy for the Kurds - have intensified in the region in the past year.
The PKK attacked police and military targets in the town of Beytussebap late on Sunday night with guns and rocket-launchers, Turkish media reported.
Nine members of the security forces were killed and a tenth died later in hospital, local officials said. A further seven soldiers were wounded.
According to the governor, the rebels appeared to have carried out a series of simultaneous attacks on checkpoints, Anatolia news agency said.
The military had responded with an extensive military offensive, Mr Ozkan was reported as saying.
Both the US and EU classify the PKK (Kurdistan Workers Party) as a terrorist organisation. It began a guerrilla campaign for an ethnic homeland in the Kurdish heartland of south-eastern Turkey in 1984.
Some 40,000 people, including many civilians, have been killed in its war with the Turkish state.
Fighting has increased in recent months, blamed partly on the turmoil in neighbouring Syria.
Ankara accuses Syria of allowing the PKK to operate on its territory although government forces have ceded control of some Kurdish areas of northern Syria to the opposition.
A month ago, rebels fired rocket launchers on a Turkish army border post in the middle of a large-scale military offensive in Hakkari province.
More recently, the PKK was blamed for a bombing in the south-eastern city of Gaziantep which left nine people dead, including four children. The PKK denied any involvement.