In light of the incident, Russia President Vladimir Putin cancelled a scheduled appearance and summoned Defence Minister, Sergei Shoigu, for a briefing on the blaze, which was under investigation.

The fire occurred while the submersible was measuring sea depths in Russia’s territorial waters, the ministry said, adding that the vessel also is used for studying the seabed. The Ministry informed that after the fire incident, the submarine was brought back to the base at Severomorsk, the home of Russia's Northern Fleet. If this information is legit, the location of the port of refuge would indicate that the sub was operating in the Barents Sea at the time of the casualty.

Minister Shoigu informed televised media

On July 1, fourteen submariners . . . died in Russian territorial waters as a result of inhaling combustion products aboard a research submersible vehicle designated for studying the seafloor and the bottom of the World Ocean in the interests of the Russian Navy after a fire broke out during bathymetric measurements.

Sources reported that the blaze marks the most serious Russian naval disaster since 2008, when 20 crewmembers died aboard the nuclear-powered Nerpa submarine in the Pacific Fleet after a firefighting system was accidentally initiated while it was undergoing sea trials.

Moreover, the Defence Ministry didn't reveal more information, as how many sailors were onboard or whether there were any survivors; This reflects that the submersible was the country's most secret one, a nuclear-powered vessel designed for sensitive missions at great depths.

In the meantime, a defence ministry source told Russian outlet RBC that the fire broke out aboard a 'descent vehicle of the nuclear project 10831 (also known as 'Losharik'),' and that the crew of the descent vehicle perished.

Sources reported that 'Losharik' is a nuclear-powered, unarmed, ultra-deep-diving submarine built for covert operations. Its capabilities are little known, but it is believed to be deployed as a payload from a heavily-modified Delta III- or Delta IV-class ballistic missile submarine. It is not administered by the Russian Navy's submarine service, but by the Main Directorate for Deep Sea Research, which functions as a separate bureau.