29 Turkish security officials including soldiers and policemen have been killed during clashes with Kurdish militants near the southeastern border with Syria and Iraq, security sources said on Monday.
At least eight other members of the security services were wounded in the fighting in the province of Sirnak, and the clashes were continuing, the sources said.
Fighting between the Turkish army and rebels from the outlawed Kurdistan Workers Party (PKK) has intensified in recent months, a development which some Turkish officials and analysts have linked to the chaos in Syria.
The militants killed five soldiers in a bomb attack on a military convoy two weeks ago. The Turkish military retaliated quickly, killing 21 rebels in an operation involving helicopter gunships.
More than 40,000 people have been killed in the conflict between the PKK and Turkish forces since the militants launched their insurgency 28 years ago with the aim of carving out a separate state in mainly Kurdish southeastern Turkey.
The PKK is listed as a terrorist organisation by Turkey, the United States and the European Union. Some Turkish officials have said the group is getting direct support from Syria's President Bashar al-Assad and Kurdish groups in Syria.
Assad, who is battling a 17-month-old uprising against his rule in which the United Nations estimates 20,000 people have been killed, has denied that Syria had allowed the PKK to operate on Syrian territory near the Turkish border.
Since June last year, nearly 800 people have died in the conflict in Turkey, including about 500 PKK fighters, more than 200 security personnel and about 85 civilians, according to estimates by think-tank International Crisis Group.
The fighting is focused in the mountainous region bordering Iraq and Iran, but the PKK has also carried out attacks in Turkish cities. Officials blamed it for a car bombing last month which killed nine people in the city of Gaziantep, near Turkey's southeastern border with Syria.