Russian troops on Tuesday stormed the last naval vessel still flying the Ukrainian flag on the Black Sea peninsula of Crimea, a regional Ukrainian defence official said. The raid on the Cherkasy trawler occurred one day after Russian forces took control of the Kostyantyn Olshanskiy, which, like the Cherkasy, had been blocked by Russian ships in western Crimea's Donuzlav Lake, defence ministry spokesman Vladyslav Seleznyov said in a statement published on his Facebook account. "The assault team is on board the Cherkasy. The crew has been barricaded inside the trawler. The assault is on," Seleznyov wrote. The spokesman wrote in an earlier post that the trawler had been surrounded by several Mi-35 attack helicopters, two cutters and a tugboat. Ukraine's new Western-backed interim leaders ordered a full military withdrawal from Crimea on Monday following the peninsula's seizure and annexation by Russia in response to last month's fall in Kiev of a pro-Kremlin regime. Russian troops and pro-Kremlin militia now control almost all of Ukraine's military bases in Crimea, having conducted three major assaults on key naval and air facilities in the past four days.