At least 20 people have died and 21 were injured in an accident on board a Russian nuclear-powered submarine.
Reports by Russian news agencies on Saturday have been confirmed by a naval spokesman.
No details have been given of the name of the submarine, or where it was located. All the Russian Pacific Fleet will say is that the submarine was not damaged and there have been no radiation leaks.
It says the submarine was on exercises at sea and 208 people were on board.
News agencies report that an anti-submarine ship, the Admiral Tributs, was providing assistance and taking some of the injured crew to port.
The Itar-Tass news agency reports there were 208 people on board at the time, 81 of whom were servicemen.
Reports say the incident occurred in the nose of the vessel. The nuclear reactor, which is in the stern, was not affected.
Russia's worst submarine disaster happened in August 2000, when the nuclear-powered Kursk sank in the Barents Sea. All 118 people on board died.
The Kremlin was harshly criticised at home and abroad for its sluggish and secretive response to the disaster.
Nine sailors died aboard a K-159 submarine when it sank in the Barents Sea in August 2003 while being towed to port for decommissioning. Only one of the seamen on board was rescued alive.
In 2005, a mini-submarine of the Pacific Fleet got snared in a fishing net, leaving the crew trapped underwater with dwindling oxygen supplies.
A British rescue team using a high-tech mini-submarine managed to extract the Russian vessel and there was no loss of life.