08:51 GMT, July 24, 2009 KHABAROVSK | Final sea trials of Russia's Nerpa nuclear-powered submarine, which was damaged in a fatal accident during previous tests, are continuing on schedule, a shipyard official said on Friday according to RIA Novosti.

The vessel resumed sea trials on July 10 in the Sea of Japan following extensive repairs.

"The resumed sea trials are going according to schedule," the official at the Amur shipyard said, without specifying when the tests would be completed.

A high-ranking defense official said on July 10 the trials would last for about 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 leased to the Indian Navy by the end of 2009.

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