Norway on Thursday announced the expulsion of 15 Russian embassy employees in Oslo, accusing them of working undercover as intelligence officers for Moscow.
"The 15 intelligence officers have been engaging in activities that are not compatible with their diplomatic status," Norwegian Foreign Minister Anniken Huitfeldt said.
She added that the Russian embassy employees had been declared "personae non gratae" and had been instructed to leave the country "shortly.”
Norway's Foreign Ministry explained that the decision to expel the 15 diplomats had been made in response to a "changed security situation in Europe, which has led to an increased intelligence threat from Russia."
Norwegian intelligence services regularly describe Russia as one of the main espionage threats to the country, which is a member of NATO and shares a 198-kilometer border with Russia in the Arctic.
In April last year, Norway expelled three Russian diplomats on suspicion of espionage, which led to the tit-for-tat expulsion of three Norwegian diplomats in Moscow.
Although not an EU member state, Norway has adopted sanctions against Russia in tandem with those introduced by Brussels.
Despite the expulsion of the Russian embassy employees, Huitfeldt stressed that Norway was "seeking to maintain normal diplomatic relations with Russia and that Russian diplomats are welcome in Norway."