MOSCOW, May 6. /TASS/. Around 100 Turkish servicemen will start training at a military center in Russia to operate S-400 missile defense systems at the end of May, a military-diplomatic source told TASS on Monday.

"At the end of May, around 100 Turkish servicemen will start training at a Russian military center to operate S-400 missile defense systems, a regiment of which will be delivered to Turkey in 2019 in accordance with the contract," the source said adding that "training will last for around five months."

Russia's military equipment exporter Rosoboronexport did not provide any comments on the matter.

The source noted that Turkish servicemen will train to operate S-400 missile together with the second group of Chinese servicemen, who started their training in the same military center in mid-March. "Simultaneous training of anti-aircraft gunners from China and Turkey will represent an unprecedented case in the history of former USSR and modern Russia," he added.

It was officially confirmed in 2017 that Russia and Turkey signed a contract on delivery of S-400 missile defense systems to Ankara.