At least 15 Turkish soldiers have been killed in clashes with Kurdish fighters in the southeast of Turkey, in one of the deadliest attacks by Kurdish fighters in recent years.
At least 23 members of the Kurdistan Workers Party (PKK), were also said to have died in the fighting, TV station CNN-Turk said on Saturday.
Media reports said the fighting took place over night on Friday in Semdinli in Hakkari province, along the borders with Iraq and Iran.
Turkey's military said in a statement that its soldiers opened fire, in response to an overnight attack by PKK fighters on a Turkish military outpost, and killed some of the fighters.
Two soldiers remained unaccounted for after Friday's attack, General Metin Gurak, who heads the Turkish general staff's press department, told the Anatolia news agency.
He said that Turkish forces had responded to the attack with artillery fire and attack helicopters, while additional forces had been dispatched to the area.
"Most of our losses were caused by heavy weapons' fire from the north of Iraq," Gurak said.
Military operation
Turkish fighter jets and artillery units also attacked a group of PKK fighters in the north of Iraq, about 10km from the station under attack, Gurak said.
Yousef al-Sharif , reporting for Al Jazeera from Ankara, said a military operation was under way in the area as a result of the attack.
"You can say that Turkey was shocked today by the news [of the soldiers' deaths] because nobody was expecting such a big attack from the PKK - 15 soldiers is a big number now in Turkey. This is, maybe, the biggest attack in recent years," he said.
The PKK, based in south Turkey and north Iraq, has been fighting for autonomy for over two decades.
Ankara blames the PKK for the deaths of more than 40,000 people since it launched its campaign for an ethnic Kurdish homeland in 1984.
Tayyip Erdogan, the Turkish prime minister, asked parliament last month to extend a mandate, which expires later this month, to launch further military operations against the PKK in Iraq.