Russia's Nerpa nuclear attack submarine, damaged in a fatal accident during tests in November last year, has successfully passed final trials, a Pacific Fleet spokesman said on Monday.

On November 8, 2008, while the Nerpa was undergoing sea trials, its onboard fire suppression system activated, releasing a deadly 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 has been cleared for final sea trials.

"A state commission has concluded that judging by the results of all trials, the Nerpa nuclear submarine is ready to enter service with the Russian Navy," the source said.

The submarine will be officially commissioned with the Russian Navy later on Monday in the town of Bolshoy Kamen in the Primorye Territory, home to the Amur shipyard Vostok repair facility which carried out the repairs.

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 of 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.

VLADIVOSTOK, December 28 (RIA Novosti)