On or about 12 August 2000, the tenth unit of the Oscar-II class, the K-141 Kursk, sank about 100 miles from the Russian port of Murmansk. At the time the boat was participating in the fleet's major summer exercises, involving about 30 other vessels. The Kursk apparently sank quickly, and did not launch distress buoys. The submarine was not carrying any nuclear weapons at the time, and there was apparently no immediate danger of radiation leaks. Considerable confusion surrounded initial reports, though apparently the Kursk shut down its two nuclear reactors after it was crippled. Although Russian Navy commander Adm. Vladimir Kuroyodev stated that there were "signs of a big and serious collision," subsequent reports cast doubt that the sub was damaged in a collision. The US Department of Defense stated that there was " no indication that a US vessel was involved in this accident." By 15 August it was generally believed that the Kursk had been damaged by an explosion on board, probably in the torpedo room.
Initial reports suggested that at least some of the crew were alive and communicating through rhythmic tapping on the hull. Rescue submarines that rushed to the Kursk reportedly found it damaged but resting upright on the seabed, at a depth variously reported as between 350 feet and 500 feet of water. Subsequent reports suggested that the submarine was listing, perhaps as much as sixty degrees. According to initial reports, as of Monday 14 August 2000 at least one rescue craft, the Kolokol, was said to be feeding power and oxygen to the Kursk. Communication links with the boat's captain, Gennady Lyachin, were reportedly restored after a day of radio silence. However, subsequent reports indicated that these initial reports were incorrect, and overly optimistic. Admiral Kuroyedov initially expressed doubts about the possiblity of rescuing the crew, stating "the chances for a positive outcome are not very high." The Russians had two India-class rescue submarines, each of which carried a pair of small rescue submarines which could reach a depth of 2,275 feet. However, these submarines and their rescue capabilities were apparently discarded by the Russians in 1995 as a cost-savings measure.