Moscow: A Russian nuclear-powered Schucka-B (NATO: Akula II) class submarine, earmarked for a 10-year lease to the Indian Navy, resumed sea trials on Friday in the Sea of Japan, a spokesperson for the Amur shipyard said. The submarine was damaged in a fatal accident during previous tests last year which resulted in the loss of lives of 20 crew and shipyard workers.

"The Nerpa nuclear submarine...has left a repair facility in the town of Bolshoy Kamen in the Primorye Territory and is headed for a series of sea trials," a spokesperson said.

The trials will continue for about two weeks, a high-ranking defense official said Friday. "The sea trials of the Nerpa nuclear submarine will continue for two weeks. All damage on the vessel found during the investigation of the accident has been repaired," the source told local media. (See: video)

Nerpa is the original name of the Akula submarine.

In a fatal accident last year, on 8 November, while the Nerpa was undergoing sea trials in the Sea of Japan, its on-board fire suppression system went off, releasing deadly Freon gas into the sleeping quarters killing three crewmembers and 17 shipyard workers.

There were 208 people, 81 of them submariners, on board the vessel at the time.

Repairs are estimated to have cost an estimated 1.9 billion rubles (about $60 million).

Post-repairs the submarine has been cleared for final sea trials. As per procedure the submarine will be first be commissioned into the Russian Navy and subsequently leased to the Indian Navy.

The submarine is expected to join the Indian Navy by the end of this year.

India has reportedly paid $650 million for a 10-year lease of the 12,000-ton K-152 Nerpa. The Schucka-B (Akula II) class nuclear-powered attack submarines are considered to be the quietest and deadliest of all Russian nuclear-powered attack submarines.