Six Turkish soldiers have been killed in an attack by Kurdish rebels near the border with Iraq, Turkey says.
The attack took place overnight on a military outpost near the town of Cukurca in Hakkari province, south-east Turkey.
Another 15 soldiers were wounded in the attack, Turkey's prime minister said. He said one rebel was shot dead, and the military was pursuing others.
Clashes have flared in the past few months after a period of relative calm.
The Kurdish Workers Party (PKK) has mounted a series of attacks on government forces since a tentative peace process broke down.
In May, imprisoned PKK leader Abdullah Ocalan said he had given up hopes of dialogue with the government.
Peace drive stalls
Tuesday's attack was one of the worst suffered by the Turkish army during a year in which dozens of soldiers have been killed.
The Turkish military has responded to the rebels' escalation by carrying out air strikes on rebel targets in northern Iraq, where several thousand PKK guerrillas are based.
Turkish Prime Minister Recep Tayyip Erdogan said the country would "pursue our struggle against terrorism with determination".
"We will continue fearlessly and tirelessly. We will not take even one small step back," he said.
Last year, the Turkish government announced an initiative to end the conflict and to address the grievances of the Kurdish minority, but the peace drive foundered in the face of strong nationalist opposition, and now seems to have been abandoned, correspondents say.
The PKK began its armed struggle against the Turkish government in 1984, calling for a Kurdish homeland within Turkey. More than 40,000 people have been killed in the resulting conflict.