"The Ukrainian Navy laid minefields on the approaches to the ports of Odessa, Ochakov, Chernomorsk and Yuzhny (about 420 mines of obsolete types of NM (anchor mine) and YRM (anchor river mine) produced in the first half of the 20th century)", the security service elaborated.
However, it was noted that sea storms in the area caused the cables connecting the mines to bottom anchors to break, thereby resulting in the bombs drifting freely in the sea. The fact that the cables broke points to the "unsatisfactory technical condition of the mines".
"Given that there a lot of southward surface currents in the vicinity of the listed Ukrainian ports, we do not rule out the possibility that the derailed mines will drift into the Bosphorus and further into the seas of the Mediterranean basin", the Federal Security Service warned.
Russia's military operation in Ukraine began on 24 February, with the Kremlin citing the goal to "demilitarise and de-Nazify" the neighbouring country. According to Russia's Defence Ministry, Russian forces only target Ukraine's military infrastructure and pose no threat to civilians.
Russia launched its military operation to support the breakaway People's Republics of Donetsk and Lugansk. Western countries have strongly condemned the operation, calling it an invasion and imposing harsh sanctions on Moscow.