MOSCOW, June 16. /TASS/. The Admiralty Shipyard in St. Petersburg in Russia’s northwest will build a series of Project 636.3 Varshavyanka-class diesel-electric submarines for the Russian Northern Fleet, a source in the domestic defense industry told TASS on Thursday.

"We expect to sign a corresponding contract for the construction of a series of six Project 636.3 submarines for the Northern Fleet next year and start implementing it in 2024," the source said.

Varshavyanka-class conventional subs have proven their worth more than once in real combat conditions and confirmed their stated operational characteristics, the source emphasized.

TASS has no official confirmation of this information yet.

The Admiralty Shipyard is completing the construction of a series of Project 636.3 diesel-electric submarines for the Russian Pacific Fleet. The shipbuilders have already built three out of six Project 636.3 subs (the B-274 Petropavlovsk-Kamchatsky, the B-603 Volkhov and the B-602 Magadan) that are already operational in the Fleet’s combat inventory.

The other three submarines are under construction according to schedule: the B-588 Ufa is set to be handed over to the Fleet this year while the Mozhaisk and the Yakutsk will be delivered to the Navy in 2023 and 2024, correspondingly.

Prior to that, the shipbuilders built a series of six Project 636.3 submarines for the Russian Black Sea Fleet. The Black Sea Fleet’s subs participated in combat operations in Syria and are actively involved in Russia’s special military operation in Ukraine.

Media reports earlier suggested that a series of three Project 636.3 submarines could be built for the Russian Baltic Fleet after the construction of these subs for the Pacific Fleet was over.

Project 636.3 submarines (NATO reporting name: Improved Kilo-II) belong to the third generation of large diesel-electric subs and are among the world's quietest underwater cruisers. They are 74 meters long and displace more than 3,900 tonnes. Due to their strong hull, these submarines have an operational depth of 240 meters and can dive to a maximum depth of 300 meters.

The submarines of this Project have an operational range of up to 7,500 miles. They are armed with Kalibr-PL cruise missiles that are launched from torpedo tubes from the sub’s submerged position.