Russian troops forced their way into a Ukrainian marine base in the Crimean port city of Feodosia early on Monday, overrunning one of the few symbols of resistance left after Moscow took control of the peninsula from Ukraine.The Russians used stun grenades and fired automatic weapons as they charged in, a Ukrainian military official said. Ukrainian flags had been taken down from flagpoles inside the base.A Ukrainian army officer, First Lieutenant Anatoly Mozgovoy confirmed to Reuters by phone from inside the compound that the the base had been taken over.”The invading troops were using stun grenades and also firing automatic weapons. The interior of the compound is full of Russian troops,” said Vladislav Seleznyov, a Ukrainian military spokesman in Crimea.Russian paratroopers also descended into the base from four helicopters hovering above, he added.Moscow formally annexed Crimea on March 21 in a move not recognised by Kiev and the West, prompting sanctions on Russia over the Cold War-era style conflict.