Four soldiers have been killed in an army helicopter crash in the northwestern province of Kocaeli.

Four soldiers have been killed in an army helicopter crash in the northwestern province of Kocaeli, the Turkish General Staff announced late on Sunday.

The S-70B Sikorsky aircraft, which took off from the Cengiz Topel Military Airport in Kocaeli, disappeared from radar after it lost connection with its base at 12:25 Turkish local time.

The wreckage of the chopper has been located in a mountainous region in the Kartepe district of Kocaeli province.

The last helicopter crash to take place in the country occurred in a rural area near the Golbasi district in the capital, Ankara, in December of last year. All four soldiers on board were killed.

Security officials have launched an investigation to uncover the cause of the crash.