Kurdish fighters have killed 13 Turkish soldiers in a clash in Turkey's southeast, and troops responded by shelling an area near the Iraqi border, according to the military.
The soldiers were killed on Sunday, after a suspected member of the PKK, the Kurdistan Workers party, was killed in earlier fighting in Sirnak province.
"One of our units serving in the Sirnak region ... was killed in an armed attack by members of a terrorist organisation," the army general staff said in a statement on its website.
"The terrorists were pursued under fire by our units to escape routes out of the country," the statement said.
Abdul-Rahman al-Chadarchi, a spokesman for the PKK, confirmed the attack and said the Kurdish fighters had sustained no casualties.
Yilmaz Akinici, a Turkish journalist who was in the area, told Al Jazeera that one of the soldeirs killed was an officer.
He said that the incident happened very close to the Iraqi border and that the PKK fighters were thought to have escaped into northern Iraq.
"We can hear the Turkish artilery shelling the Iraqi broder," he said.
About 3,000 PKK fighters, which Turkey labels as "terrorists", are based in the mountains of northern Iraq.
Violence escalates
Fighting between the PKK and the army has escalated recently in Turkey's mainly Kurdish southeast as the military steps up operations before winter, when harsh conditions slow down the rebels' movement.
Turkey has been pressing Iraq and the US to hit the PKK bases in northern Iraq, and has considered a unilateral military operation across the border to root out the Kurdish fighters.
On Sunday, the military designated 27 "security zones" in eastern and southeastern Turkey, where the borders with Iraq and Iran converge.
Starting on Tuesday, the zones will be in place until December 10 and the areas will be off-limits to civilians.
The military imposed similar zones earlier in June in three southeastern provinces to keep civilians away while the army battles the PKK.