Moscow, Jul 31 (IANS/RIA Novosti): Russian President Vladimir Putin took part in a ceremony to launch the construction of Russia's fourth Borei-class (Project 955A) ballistic missile submarine.

"By 2020, we should have eight Borei-class submarines. Two of them - the Alexander Nevsky and one other - are in trials. I am sure the entire project will be implemented," Putin said.

The ceremony for the boat, the Knyaz Vladimir, was held Monday at Sevmash, Russia's largest shipyard and sole nuclear submarine maker located in the port city of Severodvinsk on the White Sea.

More new-generation warships - both surface ships and submarines - should be built for Russia's "new-look navy", complete with advanced weapons, command and control, and communication systems, Putin said.

The Borei class is expected to become the mainstay of the Russian Navy's strategic nuclear deterrent, replacing the aging Project 941 (Typhoon class) and Project 667 class (Delta-3 and Delta-4) boats.

Three other Borei class boats are at various stages of development at Sevmash. The Yury Dolgoruky is currently undergoing sea trials, while the Alexander Nevsky and the Vladimir Monomakh are under construction.

The Borei class will be armed with the Bulava ballistic missile, which is also in the final stage of development and due to enter service on the lead vessel in the class, the Yury Dolgoruky, later this year.