At least 20 people have died and another 21 were injured in an accident on board a Russian nuclear-powered submarine, Russian news agencies said. The incident on Saturday involved the failure of a fire extinguishing
system. A naval spokesman confirmed the reports, adding that 208 people were on board.

A firefighting system went off during testing of a nuclear submarine in Russia's Pacific Fleet, a senior navy official was quoted as saying by the Russian Itar-Tass news agency.

"During sea trials of a nuclear-powered submarine of the Pacific Fleet the firefighting system went off unsanctioned, killing over 20 people, including servicemen and workers," Igor Dygalo, the Russian Pacific Fleet spokesman, said.

"The submarine is not damaged, its reactor works as normal, and radiation levels on the submarine are normal," Dygalo said. The submarine, whose name and whereabouts have not been disclosed, has been ordered to suspend sea trials and return to port in the far eastern Primorye territory, he said.

Anatoly Serdyukov, Russia's defense minister, reported the incident to Dmitry Medvedev, the Russian president, who had ordered a "full and meticulous" investigation and "all possible aid and support to the victims' families," according to the report.

An anti-submarine ship, the Admiral Tributs, was providing assistance and taking some of the injured crew from the submarine to port, news agencies reported. Russia's worst submarine disaster occurred in August 2000, when the nuclear-powered Kursk sank in the Barents Sea, 118 people on board died in the incident. 

An Akula Class Russian Submarine, same class as Vepr K-157.