Russia is in contact with Turkey regarding the S-400 anti-aircraft missile systems delivered to that country, Russian presidential spokesman Dmitry Peskov said during a press briefing Friday.

"I can only say one thing here: this topic belongs to the most sensitive domain. We [i.e. Russia] have had contacts with the Turkish side on this issue, and we will continue the contacts," the Kremlin spokesperson said.

Earlier, the Turkish pro-government Hurriyet daily reported that the S-400s Turkey had purchased from Russia had been sold to one of the Persian Gulf countries. According to the report, this deal will be announced soon.

In this regard, Peskov was asked whether Ankara had asked Moscow’s permission for this sale, and how Moscow had responded.