ST. PETERSBURG, January 23 (RIA Novosti) - St. Petersburg's Admiralty Shipyards said Tuesday it will soon begin a final round of sea trials of a fourth-generation diesel submarine.

The construction of the Project-677, or Lada-class diesel submarine, named the St. Petersburg, began in 1997 and involved a unique design developed by the Rubin design bureau.

The submarine, whose export version is known as the Amur 1650, features a new anti-sonar coating for the hull, an extended cruising range, and advanced anti-ship and anti-submarine weaponry.

A second Lada-class submarine, the Kronshtadt, which is the first in the production series, is also being built at the shipyard and will be commissioned by the Russian Navy in 2009.

A third submarine, whose keel was laid November 10 last year, is named after a city associated with Russian naval glory - Sevastopol, and is expected to be launched in 2010.

Admiralty Shipyards is a state-owned company that specializes in the design, production and modernization of civilian and naval surface ships and submarines.

Since 1910, the company has constructed 300 submarines (including 41 nuclear submarines) and 68 deep-diving and submersible vehicles. It accounts for 15% of the world submarine sales, and has built Kilo-class submarines for India, China and Iran.

Indonesia has recently expressed its desire to purchase two Lada-class diesel submarines for its Navy.