Nine Turkish military personnel were killed in a helicopter crash in the southeast of the country, the Ministry of Defence said.
A further four people were injured in the crash in the town of Tatvan, in the predominantly Kurdish-populated Bitlis province.
The helicopter took off from the Bingol province at 10:55 GMT, it said in a statement, adding that search operations were launched after it lost contact at 11:25 GMT.
It described the crash as accidental, but did not elaborate.
Turkish security forces regularly conduct operations in the country's eastern and southeastern provinces, where the Kurdistan Workers' Party (PKK) has long attempted to establish a presence. The PKK is designated a terror group by the US, EU and in Turkey.
The conflict, which began in 1984, has led to the deaths of 40,000 people, including women, children and infants.