Norway announced Thursday the expulsion of 15 employees of the Russian Embassy in Oslo, which it considers "intelligence agents," while the Russian mission described the decision as "extremely unfriendly," vowing to "respond."

"These 15 intelligence agents have been declared persona non grata for activities not commensurate with their diplomatic status," Norwegian Foreign Minister Annekin Hotvelt said in a statement.

"It is an important measure to counter and reduce the size of Russian espionage activities in Norway," she added.

The Norwegian Foreign Ministry stated that the fifteen Russians present in the country under diplomatic cover should leave the Norwegian territory "soon".

And Hotvelt stressed during a press conference that their activities had been tracked "for a while", without wanting to specify the charges actually against them.

"Our reaction is very negative," Russian embassy spokesman Timur Chekanov told AFP in an email.

"It is a new, extremely unfriendly decision, which will be followed by a response," he added.

Oslo justified its decision with "new geopolitical data that generated, in terms of espionage, an increasing threat from Russia."

The Norwegian intelligence services classify Russia and China as two major threats in the field of espionage to the NATO member state, which shares a 198-kilometer border with Russia in the Arctic.

And in April 2022, a few weeks after the start of the Russian invasion of Ukraine, Oslo, like many other European capitals, expelled three Russian diplomats suspected of espionage, prompting Moscow to respond by expelling three Norwegian diplomats.

Relations between the two countries have deteriorated greatly due to the conflict in Ukraine, after they had maintained close relations for a long time, especially in the far north.

Norway has approved almost all of the sanctions that Brussels imposed on Russia, even though Oslo is not a member of the European Union.