ANKARA, March 26. /TASS/. Two gunmen involved in the terrorist attack on a crowded event at the Crocus City Hall music venue in a Moscow suburb visited Turkey, but Moscow did not give any advance warning about these individuals, the Hurriyet newspaper reported, citing sources.

According to the newspaper, two of the four arrestees had previously traveled from Russia to Turkey and back, arriving in the country from Moscow. At the same time, they had no registration on the territory of the country: no residence permits or any other documents allowing legalization in Turkey.

The sources added that Moscow had not given any advance warning about these individuals. The facts of their stay in Turkey "are being thoroughly investigated" and will be reported to the Russian side.

The newspaper also said that "Ankara has thoroughly investigated all the issues regarding these two individuals and has informed Moscow about everything."

The Hurriyet newspaper added that the Turkish side expects Russia to increase the exchange of information on the activities of the Islamic State terrorist group (IS, outlawed in Russia) and its offshoot, IS-Khorasan, as they pose an equal threat to Turkey.