A fire onboard a top secret nuclear powered Russian Navy submarine killed 14 sailors after an unexplained accident occurred in one of the submersible’s battery compartments.

The 14 senior officers died of smoke inhalation as a result of the fire on the submersible in the Barents Sea. Though the details of the sub and its mission remain classified, the speculation is that the fire broke out while the deep-sea submarine was exploring the Arctic seabed.

The Russian Defence Ministry has named all 14 victims, all of whom were senior officers and from a unit based in Petergof, a district of St Petersburg. Among the victims were seven were first-rank captains, three second-rank captains, two were third-rank captains; one was a captain-lieutenant and one a lieutenant-colonel.

A first-rank captain comes fifth in the Russian naval hierarchy, after four ranks of admiral. After three ranks of captain comes the rank of captain-lieutenant.

Russia’s Defence Minister Sergei Shoigu said the top-secret military craft’s nuclear- reactor had been isolated from the fire and has been towed to Severomorsk in the far north of Russia.

Severomorsk was also home to the Kursk nuclear submarine, which sank in 2000 and killing all 118 sailors onboard.

The Kremlin and Russia’s traditionally tight-lipped intelligence services have given few details about the type of submarine that was involved in the incident, but several sources have identified the vessel as an AS-12 “Losharik” – or AS-31 submersible – a mini-sub can dive up to 6,000 metres and are designed to be carried under the belly of a larger submarine. They are operated by the Russian Military’s Chief Directorate for Deep Water Research – Moscow’s “underwater intelligence service”.