(RFE/RL) -- An accident aboard a nuclear Russian submarine has killed at least 20 people and injured another 21 during a test run in the Pacific Ocean.
President Dmitry Medvedev has ordered a full inquiry into the mishap, the worst involving a Russian submarine disaster since the "Kursk" sank in 2000, killing 118.
The accident took place on November 8 during sea trials of the new vessel in the Pacific Ocean.
Russian naval spokesman Igor Dygalo told reporters that the accident occurred in the Sea of Japan and was the result of the "unsanctioned" activation of the submarine's fire-extinguishing systems.
Dygalo said the dead include sailors and shipbuilders. According to the Russian Navy, 208 people were on board the submarine, but of those only 81 were servicemen; the others were naval technicians and specialists.
The injured have been taken ashore and hospitalized.
Radiation Levels 'Normal'
Dygalo said the nuclear reactor is intact and that no radiation leakage had occurred.
"The submarine is not damaged. The sections were ventilated," he said. "I stress that the main power unit, I mean the reactor section, is functioning properly. Radiation levels on the ship are normal."
Dygalo did not identify the submarine, saying only that it was to scheduled to enter full service with the Russian Navy at the end of this year. Russian media quote naval sources as saying the accident occurred aboard the "Nerpa," an attack submarine.
Dygalo gave no details of how the accidental activation of the ship's fire-extinguishing system caused the casualties.
Russian news agencies, citing unnamed sources, reported that chemicals used by the system were released by error and that the wounded were suffering from poisoning.
The incident is Russia's worst naval accident since torpedo explosions sank another nuclear-powered submarine, the "Kursk," in the Barents Sea in 2000, killing all 118 crew members.
The Kremlin, which came under fire for its sluggish response to that disaster, reacted more quickly this time.
The Kremlin's press service said President Dmitry Medvedev has ordered a thorough investigation.
And First Deputy Defense Minister Alexander Kolmakov -- together with navy chief Admiral Vladimir Vysotsky -- is on his way to the site of the accident.
String Of Accidents
Despite a major spending increase, Russia's military is still marred by decaying infrastructure, aging weapons, and corruption.
In 2003, nine seamen died aboard a K-159 Russian submarine when it sank in the Barents Sea while being towed to port for decommissioning. Only one sailor survived the incident.
In 2005, a British team rescued a Russian mini-submarine of the Pacific Fleet that had become snared underwater in a fishing net.
The latest accident comes as Russia seeks to restore its military clout amid strained ties with the West.
A Russian naval squadron is headed to Venezuela this month for joint exercises near U.S. waters.