One sailor was found dead earlier Tuesday, and twelve of the 18 members of the Sinegorye crew remain missing. Deck officer Vyacheslav Lozitsky said he believes more will be found alive.
Lozitsky said two of other four survivors are recovering from dehydration. South Korean coast guards said that they will be able to return to Russia in not less than two days.
The Sinegorye, which was sailing in the Sea of Japan 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.
Lozitsky said the vessel, which was transporting timber, sunk within one hour due to a sudden heavy storm, which caused the vessel to lurch violently. Most of the timber broke through the holds, damaging hatches and equipment, and water began to flow into the ship.
"We simply didn't have time to pump the water out," he said.
When the ship heeled to an angle of about 20 degrees, the captain ordered the crew to leave the vessel. However, only one of the two rescue boats was operational, the other being trapped under a collapsed mast, the deck officer said.
A spokesman for the regional Emergency Situations Ministry in Russia's Far East port of Vladivostok earlier said South Korea's patrol boats and an aircraft continued to search the area.
Russia's Yury Orlenko ship has left Vladivostok to join rescue efforts, and an Emergencies Ministry Be-200 amphibious plane from the city of Khabarovsk in Russia's Far East will arrive at the scene as soon as the weather permits, the official said.
Turbulent weather conditions are complicating the rescue operation, with a wind speed of 20 meters per second (45 mph) and wave height of around seven meters (23 feet), the official said.
