Russian and Ukrainian naval forces faced off in the Black Sea Sunday, with the Russian navy blocking a key waterway during the confrontation. The Ukrainian military claimed Sunday that Russian forces attacked several Ukrainian naval vessels in the Black Sea as they made their way towards the port of Mariupol in the Azov Sea as part of a planned transfer. A group of Russian vessels "carried out openly aggressive action", Ukraine claimed, and opened fire on several ships. Two Ukrainian vessels were reportedly damaged, the Berdyansk, and the Nikopol. A Russian tanker was positioned to block the Kerch Strait, barring the Ukrainian vessels' path to the Azov Sea. Russian special forces then seized three Ukrainian vessels, including two gunboats and a tugboat, Ukraine claimed. Two Ukrainians were wounded in the encounter. Ukraine also claimed that a Russian ship intentionally rammed one of its vessels. Russia has claimed that the Ukrainian vessels illegally entered Russian waters, and carried out potentially dangerous maneuvers. This year, Russia opened a 12-mile bridge across the Kerch Strait, linking the Crimean Peninsula with Krasnodar, in western Russia. Russia occupied and annexed the Crimean Peninsula from Ukraine in 2014.