The Sikorsky helicopter reportedly crashed on Herekol Mountain, in the Pervari region of Siirt province, due to adverse weather conditions. Siirt Governor Ahmet Aydın said all of the soldiers aboard the helicopter were killed in the crash.
Fourteen of the victims were members of gendarmerie special forces and the rest were helicopter staff, he said. The soldiers were being transported to a region near Turkish border with Iraq to help troops in their fight against terrorists. Aydın said three officers, four noncommissioned officers, one special sergeant and nine privates were killed in the crash.
The governor blamed the crash on heavy fog and ruled out a terrorist attack.
"The weather during the transportation [of troops] was bad. There was extreme rain. The helicopter crashed into rocks because of the fog," Aydın said in televised statements. "The incident was the result of a crash and any kind of an attack is out of the question," he added.
The General Staff said in a statement later in the day that an investigation had been launched into the crash and that the exact cause of the accident would be determined by the end of this investigation.
The Turkish military has been carrying out operations on the mountain in recent months to flush out militants from the terrorist Kurdistan Workers Party (PKK) who have hideouts there.
Since summer there has been an upsurge in PKK attacks in southeastern Turkey, notably in the Hakkari region.
Commenting on the crash on Saturday, President Abdullah Gül expressed sadness over the deaths of the soldiers who he said "were travelling on a helicopter under adverse weather conditions to help their comrades." The president also slammed terrorism. "They [terrorists] cannot bring the state into line with terror," he said, adding the incident would not deter Turkey from its determination to fight the PKK.
Turkish jets and helicopters have pounded PKK positions along the border with Iraq and Iran for three days, killing 42 terrorists, Hakkari's governor said late on Friday.
More than 40,000 people have been killed in the conflict between Turkey and the PKK, which launched its insurgency in 1984 with the aim of carving out a separate state in the mainly Kurdish Southeast of Turkey.
The PKK is designated a terrorist group by Turkey, the United States and European Union.