Ukraine says Russian forces controlling the strategic region of Crimea are demanding that the crew of two Ukrainian warships must surrender.
Ukrainian Defence Ministry spokesperson Maksim Prauta said four Russian navy ships were blocking Ukraine's anti-submarine warship Ternopil and the command ship Slavutych in Sevastopol's harbour.
He said the Russians ordered the crew to surrender within the hour or face Russians storming and seizing the ships and crew.
