K-141 Kursk was a Russian nuclear cruise missile submarine which was lost with all hands when it sank in the Barents Sea on August 12, 2000. It was named after the Russian city Kursk, around which the largest tank battle in military history, the Battle of Kursk, took place in 1943.

The Kursk sailed out to sea to perform an exercise of firing dummy torpedoes at Pyotr Velikiy, a Kirov class battlecruiser. On August 12, 2000 at 11:28 local time (07:28 UTC), the missiles were fired, but an explosion occurred soon after on Kursk. The only credible report to-date is that this was due to the failure and explosion of one of Kursk’s new/developmental torpedoes. The chemical explosion blasted with the force of 100-250 kg of TNT and registered 2.2 on the Richter scale [1]. The submarine sank to a depth of 108 metres, approximately 135km (85 miles) off Severomorsk, at 69°40′N, 37°35′E. A second explosion 135 seconds after the initial event measured between 3.5 and 4.4 on the Richter scale, equivalent to 3-7 tons of TNT [2]. Either this explosion or the earlier one propelled large pieces of debris far back through the submarine.

Kursk was eventually raised from her grave by a Dutch team using the barge Giant 4, and 115 of the 118 dead were recovered and laid to rest in Russia. Russian officials have strenuously denied claims that the sub was carrying nuclear warheads. When the boat was raised by a salvage operation in 2001 there were considerable fears moving the wreck could trigger explosions.

via ru_warhistory