A total 35 people, including 12 soldiers, were killed as the Turkish military clashed with Kurdish rebels near the border with Iraq and Iran, the BBC reported on Sunday.
Turkish soldiers were ambushed in the area early in the day, prompting the army to dispatch reinforcements.
Kurdistan Workers' Party (PKK) has been blamed for the attacks, which also left an unspecified number of troops wounded, while a pro-rebel website said claimed some Turkish soldiers had been taken hostage.
The clashes come just days after the Turkish parliament gave the military permission to cross into north Iraq if in pursuit of Kurdish rebels.
Thousands of PKK fighters are believed to use northern Iraq, where Kurds are a majority, just as in some areas of southeastern Turkey, as their main base of operations.
Even though Kurdish authorities in the north of Iraq claim they are not helping the organisation, PKK has long used the mountainous region as the staging area for its attacks over the decades in its fight to win the Kurds a wider autonomy in Turkey.