SAINT PETERSBURG, March 28 (RIA Novosti) - The fourth Russian Varshavyanka-class submarine for delivery to the Vietnamese navy has been launched in a ceremony at the shipyard where it was built, St. Petersburg city officials said Friday.
Vietnam signed a contract in 2009 to buy six of the diesel-electric submarines - dubbed "black holes in the ocean" by US navy officials for their near invisibility - in a deal reportedly worth $2 billion.
Analysts saw the purchase as a move to counterbalance China's expanding maritime influence in the region.
Two of the submarines have already been delivered to Vietnam, with the third currently undergoing sea trials and another now under construction at St. Petersburg's Admiralty Shipyards.
The Varshavyanka class (Project 636) is an upgrade to the Kilo class, featuring advanced stealth technology, extended combat range and the ability to strike land, surface and underwater targets.
The boats, which can be armed with torpedoes, mines, and Kalibr 3M54 cruise missiles, are mainly intended for anti-shipping and anti-submarine missions in the relatively shallow waters of littoral zones.
The submarines have a displacement of 3,100 tons, can reach speeds of some 20 knots, dive to 300 meters and are manned by 52 crew members.