ANKARA, Turkey (AP) — A military helicopter crashed in eastern Turkey on Thursday, killing nine soldiers on board and injuring four others, the Defense Ministry said.

The helicopter crashed in the town of Tatvan, in the predominantly Kurdish-populated Bitlis province. It wasn’t immediately clear what caused the crash.

The Cougar type helicopter was on its way to Tatvan from the nearby province of Bingol when it disappeared from radar at 2:25 pm (1125 GMT), the ministry said. The injured soldiers were being evacuated to hospitals, it added.

The location is in an area where Turkish troops have been combating militants of the banned Kurdistan Workers’ Party, or PKK.

The conflict has killed tens of thousands of people since 1984. The PKK is considered to be a terrorist group by the United States and the European Union.