Kurdish rebels have killed at least 16 Turkish soldiers in an attack in the south-eastern province of Hakkari, Turkey's military has said.
Bombs were said to have been detonated near two military vehicles in the village of Daglica on Sunday evening.
Turkish jets carried out several air strikes on Kurdistan Workers' Party (PKK) targets on Monday in retaliation.
There has been a surge in violence between the army and the PKK after a ceasefire collapsed in July.
The PKK said it was behind the attack. Initially it said 15 soldiers had been killed, but later raised the figure to 31.
But the Turkish army said on Monday that 16 soldiers died, while six were injured.
President Recep Tayyip Erdogan said he was saddened by the attack and promised a "decisive" response.
"The pain of our security forces who were martyred in the treacherous attack by the separatist terrorist organisation sears our hearts," he said.
After his comments, about 200 people chanting pro-Erdogan slogans attacked the offices of Turkish newspaper Hurriyet in Istanbul.
They accused the news organisation of misquoting Mr Erdogan and implying that he was trying to gain political capital from the Daglica attack.
Hurriyet has attracted criticism from pro-government circles over its coverage of the conflict between Turkey's government and the PKK.
The government says military operations against the Kurdish rebel group will continue until it withdraws from Turkish soil and disarms.
Curfews have been imposed in several towns where clashes take place and over a hundred districts have been declared "temporary security zones".
In response, several municipalities in the predominantly Kurdish east and south-east of Turkey have announced "self-rule".
Critics accuse President Erdogan of renewing violence to curb the support for the pro-Kurdish People's Democratic Party (HDP), whose 14% share of the vote in June elections cost the governing AKP its majority in parliament.
The government denies these accusations. Many people fear the clashes will mount as snap elections scheduled for November draw closer.
More than 40,000 people have died since the PKK launched its armed campaign in 1984.