Russia's navy says a seven-man crew trapped in a small submarine on the Pacific Ocean floor has only 24 hours of air left.
Naval officials earlier said there was up to a five-day supply of air in the submarine, nearly 200 meters undersea off the Kamchatka Peninsula in Russia's far east. But a revised assessment says there is a one-day supply.
U.S., Russian and Japanese vessels are on the way to attempt to rescue the crew. The Russian news agency, Interfax, says the Japanese rescuers will not arrive at the scene until Monday.
Russian officials say the deep-sea observation vessel became tangled in a fishing net on the seabed about 75 kilometers from the port of Petropavlovsk-Kamchatsky Thursday. The sailors are said to be in good condition.
The undersea drama has revived memories of a Russian nuclear submarine Kursk that sank in the Barents Sea after an explosion five years ago. All 118 men on board that sub died.
Information for this report is provided by AP and Reuters.