The Russian Defence Ministry revealed the blaze engulfed the vessels on Monday while it was performing tests.
In a statement, the Ministry praised the courage of the sailors aboard, saying the fire was extinguished thanks to the crew’s “self-sacrifice”.
It also said the submarine is now at the Arctic port of Severomorsk, the main base of Russia’s Northern Fleet.
The official statement read: “On July 1, a fire broke out in Russian territorial waters on a research deep-water apparatus designed to study the bottom space and the bottom of the World Ocean in the interests of the Russian Navy.
“During the biometric measurements, 14 submariners died as a result of burning with poisoned products.
“The causes of the incident are established.”
Officials added an investigation has been launched by the Commander-in-Chief of the Navy.
MORE TO FOLLOW