Russia is increasing its naval operations in the Pacific region, with plans to base additional nuclear submarines in the area by 2024, according to the state-linked Tass agency.
Tass did not say where the bases would be, but Russia has a naval base at Vladivostok, which has been in operation for more than 100 years. It also has an existing Pacific Fleet base that can host nuclear submarines on the Kamchatka Peninsula.
Russia already has nuclear submarines that can stay submerged for months, including new Borey class vessels, at least three of which are scheduled for deployment in the Pacific region.
The Borey class can carry 16 submarine-launched Bulava ballistic missiles. Each Bulava can carry six 140 megatonne nuclear warheads. By comparison, the bomb that killed about 80,000 people when it was dropped on the Japanese city of Nagasaki in the Second World War was 18 kilotonnes.
The bases could also house submarines capable of launching a nuclear-capable drone torpedo.
The Poseideon torpedo is about 24 metres long, according to the US Naval Institute, and has been described as a nuclear-armed drone that also relies on nuclear-powered propulsion, enabling it to reach targets thousands of kilometres away from its launching point.
Little is known about the Poseidon's warhead, but experts say it could have a yield of two megatonnes, which would give the weapon around 100 times the destructive power of the bomb dropped on Nagasaki.
The torpedoes are being developed for deployment on the Belgorod and Khabarovsk nuclear submarines, Tass reported.
Russia said it was working on building 30 of the devices.
“Work on the construction of coastal infrastructure facilities for basing two special submarines in Kamchatka is planned to be completed early next year,” Tass cited a defence source as saying.
The Pacific Ocean and the Sea of Okhotsk make up the Kamchatka Peninsula's eastern and western coastlines.
The source told Tass that a new division was being formed as part of the Submarine Forces of the Pacific Fleet, which will include not only Belgorod and Khabarovsk but also other submarines.
The new special-purpose submarines will participate in solving the tasks “of strategic deterrence”, the source said.
Russia's major upgrade of the nuclear base comes amid rising US-China tensions over influence in the Western Pacific.
Mr Putin said on Sunday that Moscow was not creating a military alliance with Beijing, but both he and Chinese leader Xi Jinping pledged closer ties, including in the military sphere, during their meeting last week.
With reporting from agencies