Seven Kurdish rebels and six Turkish police officers have been killed in clashes in the far south-east of the country, reports say.
Turkish forces launched a large-scale operation against the Kurdish Workers’ Party (PKK) near Mount Cudi, in the province of Sirnak, on Wednesday.
Helicopter gunships were used in this, the largest attack on rebels in 2012.
Correspondents say the fighting was sparked by tensions surrounding the Kurdish New Year celebrations, Novruz.
Five of the officers died on Wednesday, while another was killed on Thursday, security officials said.
One rebel is reported to have been captured in the operation, which involves both army troops and special operations police forces.
On Sunday, police in the south-eastern city of Diyarbakir used tear gas and water cannon to prevent thousands of Kurds from holding a demonstration timed to coincide with Novruz. The unrest later spread to other Turkish cities.
PKK rebels recently have stepped up their operations, BBC’s correspondents say.
The rebel Kurdistan Workers’ Party (PKK) has been fighting for autonomy in Turkey’s largely Kurdish south-east since 1984, in a conflict that has claimed tens of thousands of lives.
