MOSCOW, July 2./TASS/. Russian President Vladimir Putin has instructed Defense Minister Sergei Shoigu to fly to Severomorsk to ensure a thorough investigation into the reasons behind the fire aboard a Russian navy submersible.

"I ask you to fly to Severomorsk in order to personally listen to the reports and to aim the commission to get to the bottom of the causes of the tragedy," Putin told the defense minister.

"I ask you to report to me personally upon your return," Putin said.

The President offered his deep condolences to the families of the sailors killed in the fire and ordered to provide any assistance possible to them.

"I offer my sincerest condolences to the families of those killed. Everything possible must be done to help and support them," the president said at a meeting with Sergei Shoigu on Tuesday.

The president stressed that the tragedy had occurred on board an uncommon research vessel. "The crew were top professionals. According to your early reports seven among the 14 casualties were captains I rank, two were heroes of Russia," Putin said. "This is a big loss for the fleet, for the army in general," the president emphasized.

Fourteen submariners died in a fire that broke out in a submersible vehicle in Russian waters on July 1, the Defense Ministry said in a statement released on Tuesday.

"On July 1, fourteen submariners died in Russian territorial waters as a result of inhaling combustion products aboard a research submersible vehicle" after a fire broke out on board as it was conducting bathymetric measurements, the statement says.

The fire was extinguished "thanks to the self-sacrificing actions of the team," the statement says.