Ukraine’s military said on Saturday that it sank a submarine belonging to Russia’s Black Sea Fleet in an attack on the port of Sevastopol in Russian-occupied Crimea. The attack also damaged a Russian S-400 air defence system, the General Staff of the Ukrainian Armed Forces said. “The submarine sank immediately,” it said. There was no immediate comment from Moscow on the claim. The Rostov-on-Don diesel-powered submarine was launched in 2014 and can launch land-attack cruise missiles. Ukraine has hit the Russian Black Sea Fleet hard, with repeated attacks on the ports of occupied Crimea in recen…