The head of the Russian Navy, Admiral Vladimir Masorin, said the fire was probably caused by a short circuit. He said the two sailors died from carbon monoxide poisoning.
Interfax reported that the incident poses no radiation threat.
The Russian news agency said the fire erupted on the night of September 6 in a mechanics room and was put out by around midnight.
It said that the submarine belongs to Russia's Northern Fleet, and it was being towed to the port of Vidyayevo, a base for Russian submarines in the Barents Sea.
Russia's advanced S-300 air-defense system (epa file photo)
BOOM TIMES: In 2005, Russia sold more than $6 billion in weapons to more than 60 countries around the world. The state arms exporter says it has $17 billion in orders in hand....(more)