Twelve of the 18 crew members of the Sinegorye remain missing.
The ship is thought to have sunk in the Sea of Japan, according to the Russian Transportation Ministry. The Sinegorye, which was sailing around 80 nautical miles off South Korea's east coast, sent out an SOS at 1:40 p.m. local time (6:40 a.m. Moscow time/2.40 a.m. GMT) Monday, before communications were lost.
A spokesman for the regional Emergency Situation Ministry in Russia's Far East port of Vladivostok said South Korea's patrol boats and an aircraft are continuing to search the area.
Russia's Yury Orlenko ship has left Vladivostok to join rescue efforts in the area, along with an Emergencies Ministry Be-200 amphibious plane, which took off from the city of Khabarovsk in Russia's Far East at 8.10 a.m. Moscow time (4.10 a.m. GMT), the official said.
Bad weather conditions are complicating the rescue operation, with wind speed of 20 meters per second (45 mph) and wave height of around seven meters (23 feet), the official said.
