VLADIVOSTOK, July 30 (RIA Novosti) - The second stage of new sea trials of Russia's Nerpa nuclear attack submarine, damaged in a fatal accident during previous tests, will start on July 31, a subsidiary of the Amur shipyard said on Thursday.

The vessel resumed sea trials on July 10 in the Sea of Japan following extensive repairs. The first stage of new sea trials was successfully completed on Monday.

"The start of [the second stage] sea trials has been set for July 31," said an official at the Vostok repair facility in the town of Bolshoy Kamen in the Primorye Territory, where the sub is currently docked.

The source said some equipment for performance checking and adjustment work had been installed on board the submarine and the new trials will last for at least two weeks.

On November 8, 2008, while the Nerpa was undergoing sea trials in the Sea of Japan, its on-board fire suppression system went off, releasing a deadly gas into the sleeping quarters. Three crewmembers and 17 shipyard workers were killed. There were 208 people, 81 of them submariners, on board the vessel at the time.

Following the repairs, which cost an estimated 1.9 billion rubles ($60 million), the submarine was cleared for final sea trials before being commissioned with the Russian Navy, and will be leased to the Indian Navy by the end of 2009 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.