The trials were part of the manufacturer's tests and the sub is now ready for final inspection by a state commission before it enters service with the Russian Navy.

"All systems of the submarine performed well, and the problems revealed during previous tests have been resolved," a Sevmash spokesman said.

The Yury Dolgoruky is 170 meters (580 feet) long, has a hull diameter of 13 meters (42 feet), a crew of 107, including 55 officers, a maximum depth of 450 meters (about 1,500 feet) and a submerged speed of about 29 knots. It can carry up to 16 ballistic missiles and torpedoes.

Construction costs totaled some $713 mln, including $280 mln for research and development.

Three other Borey class nuclear submarines, the Alexander Nevsky, the Vladimir Monomakh, and Svyatitel Nikolai (St. Nicholas) are in different stages of completion. Russia is planning to build eight of these subs by 2015.

Fourth-generation Borey class nuclear-powered submarines are expected to constitute the core of Russia's modern strategic submarine fleet.

The submarine's entry into service could be delayed however by a series of setbacks in the development of the troubled Bulava submarine-launched ballistic missile (SLBM), which has officially suffered seven failures in 12 tests.

The future development of the Bulava has been questioned by some lawmakers and defense industry officials, who have suggested that all efforts should be focused on the existing Sineva SLBM.

But the Russian military has insisted that there is no alternative to the Bulava and pledged to continue testing the missile until it is ready to be put into service with the Navy.