"It is a big loss for the navy, and for the army as a whole," Putin told Defence Minister Sergei Shoigu in a televised meeting.

The 14 officers died from inhaling toxic gases on Monday after a Russian navy deep-sea research submersible caught on fire, the defence ministry said Tuesday.

Although the name of the vessel was not made public, the media speculated it was a highly secret AS-12 deep-water submarine. Putin did not confirm the type of vessel but said it was unusual.

"It is not an ordinary vessel, as we know, it's a scientific-research vessel, its crew is highly professional," Putin said, adding that the victims included seven Captain First Rank officers — the highest possible for staff officers in the Russian navy.

"I offer most sincere condolences to the families of the victims," Putin said, ordering Shoigu to travel to the northern town Severomorsk, where the submersible has been docked.

"I ask you to go to Severomorsk to personally hear reports and direct a commission to define the causes of this tragedy.