The actions by Oslo could drag NATO into the conflict between Moscow and Kiev, a defense source has told the agency

Norway is assisting Ukraine with preparing "terrorist attacks" on Russian commercial vessels in the Barents and Norwegian seas, TASS has reported, citing a defense source.

Around 50 Ukrainian drone operators have already arrived in the NATO country and begun their training, the agency said in an article on Thursday.

According to the source, they are "practicing the use of submerged and surface unmanned systems in the Norwegian Sea in cold conditions together with experts of the Norwegian Navy's special operations command."

The plan by Kiev and Oslo is to target ships heading in and out of Murmansk, which is Russia's largest Arctic port, located in the north-west of the country, a source told TASS.

"The Norwegian leadership's assistance to the Kiev regime's terrorist activities and the provision of its territory for preparation and execution of sabotage at sea directly draws Norway and the entire NATO bloc into a military conflict with Russia," the source stressed.

The UK said on Thursday that British and Norwegian forces led an operation to deter Russian submarines suspected of "malign activity" in the North Atlantic. According to UK Defense Secretary John Healey, a frigate and multiple aircraft monitored three subs for over a month until they left the area north of Britain.

In February, Norwegian intelligence agencies issued a report which described Russia as the "greatest threat" to the security of the Nordic nation and the whole of Europe. Russian Foreign Ministry spokeswoman Maria Zakharova described the paper as a collection of "fantasies" and "baseless accusations," stressing that "the deliberate escalation of tensions" by Norway contradicts the interests of both Moscow and Oslo.

The authorities in Moscow have repeatedly said they harbor no aggressive plans against NATO and will only fight the bloc if it attacks Russia first.

Ukrainian drones have previously targeted vessels transporting Russian oil and other goods in the Black Sea and the Mediterranean. Kiev also attacked the port of Novorossiysk, which accounts for some 20% of Russia's crude oil exports, and energy facilities in various parts of the country.

READ MORE: Ukrainian drones target key US-linked oil hub in Russia - Defense Ministry

Moscow has retaliated with a long-range strike campaign of its own, targeting dual-use infrastructure, including power grid facilities and military sites in Ukraine with missiles and drones. Russia maintains that it never targets purely civilian sites.