MOSCOW, July 29 (RIA Novosti) – The first of six Russian submarines, dubbed by the US Navy as “black holes in the ocean” because they are nearly undetectable when submerged, will be delivered to Vietnam in November, the shipbuilder said Monday.

The Varshavyanka class (Project 636M) of diesel-electric submarines have very low noise emission and can hit targets at long distances without being detected by an enemy’s anti-submarine warfare assets.

“We are expecting the signing of the acceptance act and the sub’s sailing to Vietnam in November,” the press service of Admiralty Shipyards said from St. Petersburg.

The submarine successfully completed 100-day sea trials in July while the Vietnamese crew has been in training since April this year, the shipbuilder said in a statement.

“The vessel showed excellent maneuverability and reliable work of all mechanisms during the trials,” the statement said.

Vietnam ordered a fleet of six Russian-made submarines in 2009, seen as an effort to counterbalance China’s expanding maritime influence in the region. The contract, which also stipulates the training of Vietnamese submarine crews in Russia, is reportedly worth $2 billion.

All six boats are being built at Admiralty Shipyards. They are due for delivery by 2016.

The Varshavyanka class is an improvement on the Kilo, with more advanced stealth technology and an extended combat range. The vessels displace 3,100 tons, reach speeds of 20 knots, can dive to 300 meters and carry crews of 52 people.

The submarines, which feature 533-milimeter torpedo tubes and are armed with torpedoes, mines and Kalibr 3M54 (NATO SS-N-27 Sizzler) cruise missiles, are mainly intended for anti-shipping and anti-submarine missions in relatively shallow waters.