Five Turkish soldiers have been killed in an attack by suspected Kurdish rebels, officials say.
At least six others were reportedly wounded in the attack, in Turkey's south-eastern Hakkari province.
It is the most serious loss of life for the Turkish army since six soldiers died in a bomb attack in early July.
Kurdish rebels have stepped up their campaign of attacks on civilian and army targets in the past few months.
The attack happened in the early hours of Friday near the town of Semdinli, which is close to the country's borders with Iran and Iraq.
Private CNN-Turk television said a powerful explosion was set off before rebels opened fire on the soldiers. The rebels made their escape by fleeing into the mountains.
A number of the injured soldiers were reportedly airlifted by helicopter to a military hospital in the main provincial town of Hakkari.
Security forces have launched an operation to catch the rebels.
The attack came only hours after Kurdish rebels freed a Turkish soldier they had held for more than three weeks.
The separatist Kurdistan Workers' Party, known as the PKK, has been fighting the government since 1984 in a campaign to create a Kurdish homeland in the south-east.
More than 37,000 people have been killed since then.
The rebels declared a unilateral truce in 1999, but ended it in 2004, saying Turkey had not done enough to meet their demands.