In a press statement on Saturday, Russia's Federal Security Service (FSB) said that Ukrainian naval forces had placed lines of mines near the ports of Odessa, Ochakov, Chernomorsk, and Yuzhny, reported state-run news agency TASS. The FSB said the mines were made in the first half of the 20th century by the Soviet Union.

It said the cables that connected the mines to the anchors had broken due to storms, and the mines were now being pushed along by winds and currents and freely drifting in the western Black Sea. The FSB added that it is feasible the mines could float toward Bosphorus and the Mediterranean Sea given the current direction of the currents.

The FSB said that Ukraine was to blame for placing the mines and that the Ukrainian forces have shown "utter ignorance" of international laws, and disregard for human lives.

The Russian Black Sea Fleet had on March 18 issued a mine hazard warning, TASS reported.