Twenty people were killed and 21 injured in an accident aboard a Russian nuclear submarine, the navy said on Sunday.
It is the worst accident on a nuclear submarine since the 2000 sinking of the Kursk.
Below is a timeline of Russia's main naval accidents since the collapse of the Soviet Union in 1991:
* Aug 12, 2000 - The Russian Oscar-II class submarine Kursk with 118 crew members sinks to the bottom of the Barents Sea after possibly a collision and two explosions on board.
* June 16, 2000 Toxic fuel leaked from a ballistic missile and poisoned several servicemen at a naval base in Russia's Far East.
* Aug. 28, 2003 - Russia's K-159 nuclear submarine sank while being towed to a shipyard. Nine crew were killed.
* Feb. 2004 - Dressed in full naval uniform Russian President Vladimir Putin travelled to the Arctic to watch naval exercises but the focus -- a ballistic missile launch -- failed.
* Aug. 2005 - The British navy rescued seven Russian sailors trapped in a sunk mini-submarine off Russia's Pacific coast.
* Sept. 6, 2006 - Fire on board the Viktor-3 class Russian navy submarine St. Daniel of Moscow, moored near the Finnish border, kills two crew members. A few hours later a missile launch failed.
* Nov. 8, 2008 - Twenty people died and 21 were injured on board the Nerpa, classified by NATO as an Akula-class attack submarine, when its fire extinguishing systems unexpectedly went off during sea trials in the Pacific.