MOSCOW — Russia's Ministry of Defense says 14 sailors were killed when a nuclear-powered submarine caught fire while it was underwater last week.
The vessel was a AS-12 Losharik submarine, Russian media outlet RBC reports, citing anonymous sources.
The AS-12 can reach depths of up to 6,000 meters.
Its nuclear reactor is isolated and operates autonomously.
The vessel is carried beneath the hull of the nuclear-powered submarine Orenburg to avoid detection, according to Russian newspaper Novaya Gazeta.
Russian News Agency TASS cited a statement by the Russian Ministry of Defense as saying that the submarine was in Russian territorial waters and was studying the seafloor.
The statement added that the sailors died as a result of inhaling combustion products on the vessel.
The exact cause of the fire is unknown.
Russia's President Vladimir Putin cancelled a planned visit and extended condolences to the family members of the victims, RBC reports.
According to TASS, President Putin ordered a thorough investigation to determine the cause of the submarine fire.