The submarine was put into service despite a fatal accident during its sea trials in November 2008. Earlier reports said it had passed final tests successfully.

“Additional adjustments are planned for the Nerpa in February 2010 to rectify the flaws revealed during the latest tests,” a ministry official said, as quoted by RIA Novosti.

On November 8th 2008, while the Nerpa was undergoing sea trials, its onboard fire suppression system activated, releasing frion gas into the sleeping quarters. Three crewmembers and 17 shipyard workers were killed. There were 208 people, 81 of them submariners, onboard the vessel at the time.

Following repairs, which cost an estimated 1.9 billion rubles ($65 million), the submarine was cleared for final sea trials.

The submarine will be subsequently leased to the Indian Navy under the name INS Chakra. India reportedly paid $650 million for a 10-year lease on the 12,000-ton K-152 Nerpa, an Akula II class nuclear-powered attack submarine.

Akula II class vessels are considered the quietest and deadliest of all Russian nuclear-powered attack submarines.