Ukraine on Monday said it sank two Russian naval vessels in the Black Sea with drone strikes, as explosions rang out once again in Russia’s border region of Belgorod and heavy fighting continued in eastern Ukraine.

Ukraine released video footage of what it said were armed drones hitting two patrol boats near Snake Island. Ukraine’s military said in recent days that it carried out several airstrikes on the strategic island, located 22 miles off the Ukrainian coast, destroying the air-defense system and other heavy weapons of the Russian military unit that occupies it.