Fourteen crew on board a Russian defense ministry submersible were killed after a fire broke out Monday, the ministry was quoted as saying by Russian news agencies.

The deep-sea research vessel was carrying out a military survey in Russian territorial waters, it was quoted as saying.

The ministry said in a statement Tuesday that the fire was extinguished thanks to the crew's self-sacrifice.

The submersible is now at the Russian Northern Fleet's base in Severomorsk on the Barents Sea, and an investigation has been launched to establish the cause, Interfax, RIA and TASS quoted the ministry as saying.

The ministry didn't say how many crew members were on board when the fire erupted and if there were any survivors. It didn't give a cause for the fire or provide any additional information about the incident, saying that an official investigation is underway.

The ministry's statement said the submersible is intended for studying the seabed, but didn't give its name or type.

The Russian navy uses Priz-class and Bester-class deep water vehicles, which have a hull built of titanium and are capable of operating at a depth of 1,000 meters (3,281 feet). They are transported to the area of operation by a carrier vessel and can operate autonomously for up to 120 hours.

The blaze marks the deadliest Russian naval incident since 2008, when 20 died when a firefighting system was accidentally initiated while the Nerpa nuclear-powered submarine of Russia's Pacific Fleet was undergoing trials.

In the deadliest naval incident in post-Soviet Russia, the Kursk nuclear submarine exploded and sank on Aug. 12, 2000, during naval maneuvers in the Barents Sea, killing all 118 crewmembers.