International media and officials are calling it the worst submarine disaster since the sinking of the Kursk submarine in 2000.

Russian Naval spokesman, Captain Igor Dygalo, said 208 people were aboard the submarine when an accident involving the activation of a fire extinguishing system occurred during sea trials.  No radiation accidents have been reported. Of those 208 aboard, 81 of who were naval servicemen.

Of the 20 who died in the accident, 17 where civilian specialists, Interfax Russian News Agency reported. The remaining three were officers of the Pacific Fleet naval crew that was to inherit the boat after sea trials were complete.

Twelve of the civilian dead were from Komsomolsk-na-Amur, where the vessels was built, another three were from Moscow and the remaining two were residents of the Far Eastern Primorye region, Interfax said.

According to Bellona’s Alexander Nikitin, a former submarine captain and naval nuclear safety inspector, it would be routine for many other observers beyond naval personnel aboard a vessel for sea trials.

The accident occurred somewhere in the Sea of Japan, but sources would not be more specific. The fire extinguishing system, which uses an anti-oxidant to reduced oxygen content in the air to extinguish the fire, apparently hit the crew and observers unaware. According to Nikitin, it would be mandatory for those on the submarine to have access to independent oxygen supplies in the event of a release of the fire containment unit.

Navy’s chief spokesman says no radiation leaks
Dygalo said the nuclear reactor was intact and radiation levels were normal. Twenty-one injured people have been evacuated from the submarine, Pacific Fleet sources told the State-owned RIA Novosti.

"I declare with full responsibility that the reactor compartment on the nuclear-powered submarine is working normally and the radiation background is normal," he said, quoted by Itar-Tass news agency.

Though Dygalo said the vessel that was being tested was to be put into the service of the Russia fleet, he did not release the class of the submarine, nor give specifics of where the fatal accident occurred. Russian press reports indicate that the vessel is most likely the Nerpa submarine, which the Russian Navy has been testing for lease to the Indian Navy.

Worst death toll on a Russia sub since the Kursk
The death toll of this accident makes it the worst mishap for the accident-prone Russian navy since the Kursk nuclear submarine sank in the Barents Sea in 2000 during execercises, killing all 118 sailors –this despite a week-long attempt by the Russian navy to free survivors after a crippling blast in the submarine’s torpedo compartment.

After Russia failed, Dutch and Norwegian rescue teams who had gathered at the site of the accident where finally allowed by the Russian government to help, and opened in a half an hour an escape hatch that Russia rescuers for seven days could not.

Dygalo told the BBC that both sailors and shipyard workers died in the incident, which occurred during sea trials.

Japan conducting its own radiation surveys
Japan will also be conducting an investigation of the event, given the apparent proximity of the accident to its shores.

“The Japanese reaction will be, primarily the gathering of sea water samples and air in the assumed area of the submarine for analysis and confirmation of Russian announcement that there was no damage to the submarine’s reactor,” said a Russian Naval source. 

Contradictory reports on which sub was involved
Dygalo has not yet released the name or class of the submarine, but a source within the Amur Shipbuilding Enterprise told the State-owned RIA Novosti news agency that the vessel was the K-152  – the Nerpa – a Project 971 Shchuka-B attack submarine – classified as an Akula by NATO.

But the RIA Novosti story could not be independently confirmed.

The Nerpa set to sea for trials late last month, and was reportedly intended to be leased to India when it set to sea for tests. The Nerpa has been modernized in recent years. Construction of the Nerpa was started in 1991 but funding dried up during the economic chaos of the Yeltsin years.

The Russian Navy however, has said it has no intention of leasing the Nerpa, or any other submarine, to anyone – contradiction RIA Novosti’s reports. The last time the Russian navy considered leasing submarines was in the 1980s, and the deal would have involved Charlie Class submarines had it gained traction.

Military prosecutors are investigating the incident, Dygalo told the BBC.

Russian news agencies reported that an investigative group led by Alexander Morkitsyn, first deputy to Russia’s chief military prosecutor, Sergei Fridinsky, has been dispatched from Moscow, prosecutor’s spokesman Mikhail Yanenko said. 

Sea trials end and rescue vessels bring the sub in
The vessel has been ordered to cease sea trials, and is returning to a port in the Far East Primorye region, which has similarly not been disclosed.

The Russian destroyer, the Admiral Tributs, was providing assistance and taking some of the injured crew from the submarine to port, RIA Novosti reported.

Dygalo did not say where the ships were but the Tributs is normally based at Vladivostok, Russia’s main Far Eastern naval port. RIA Novosti said it would take about 10 hours for the destroyer to reach the coast.

Dygalo said the afflicted submarine was able to move under its own power, but was being accompanied by the Sayna rescue vessel.

RIA Novosti reported the incident occurred in the nose of the vessel, citing a highly placed navel source.  The nuclear reactor, which is in the stern, was not affected.

Russian President Dmitry Medvedev is being kept fully informed about the incident, his press service said in a statement.

Deputy Defence Minister Alexander Kolmakov and Navy Commander-in-Chief Vladimir Vysotsky are flying to the scene of the incident, the BBC said.

Other Russia submarine accidents in last eight years
In August 2003, the derelict submarine the K-159 sank while being towed from Gremikha to Polyarny for dismantlement when the tow line from the tug boat hauling it snapped in heavy weather, killing nine of the 10 crew members on board. The accident also plunged 800 kilograms of spent nuclear fuel to the ocean floor 238 metres below.

The Russia government has been promising to raise the wreckage ever since, but no operations have as yet been set into motion.

In another accident in August 2005, seven Russian sailors were freed with help from a British rescue crew after three days trapped inside an AS-28 mini-submarine 200 metres down in the Pacific with dwindling air supplies.