COPENHAGEN, DENMARK -- Norway's government said Thursday that it was expelling 15 Russian diplomats from the country, saying they were suspected of spying while working at the Russian Embassy in Oslo.

Foreign Minister Anniken Huitfeldt said the move was "an important measure to counter and reduce the scope of Russian intelligence activities in Norway, and thereby secure our national interests."

The Russians declared persona non grata "must leave Norway within a short time," Huitfeldt said, adding: "We will not grant visas to intelligence officers who apply for a visa to Norway."

The minister declined to say whether the government was acting in response to a specific incident, referring questions to Norway's domestic security agency PST for details. The government said the activities of the expelled diplomats were "incompatible with their diplomatic status."

"We are not talking about regular diplomats, but intelligence officers under diplomatic cover. Their activities are a threat to Norwegian interests," Huitfeldt said.

Norwegian newspaper VG described Thursday's expulsions as the most the Scandinavian country has ordered at one time involving Russian diplomats.

The Russian Embassy in Norway called the Norwegian government's decision "an extremely unfriendly step" and promised Moscow would take "retaliatory measures," which in such a case typically involve in-kind expulsions.

Huitfeldt reacted during an afternoon news conference, saying: "Russia has no reason to respond. We have Norwegian diplomats stationed in Russia, but none of them are undercover intelligence officers."

She called Russia "an unpredictable neighbor" and "many European countries in the past year have expelled hundreds of Russian intelligence officers under diplomatic cover."

At the same time, she stressed that the government in Oslo wants "normal diplomatic relations with Russia, and that Russian diplomats are welcome in Norway"

"We do not want people who claim they are diplomats and who are actually are intelligence officers," she said. "We cannot accept that."

NATO-member Norway has a 198 kilometre-long (123-mile) border with Russia in the Arctic.

VG said that including the expelled diplomats, Russia had about 40 people working at its missions in Norway, which include the embassy in Oslo and consulates in Kirkenes and Barentsburg.

Barentsburg, located on the remote Arctic archipelago of Svalbard, is a Russian coal-mining town of about 500 people. Under a 1920 treaty, Norway has sovereignty over the archipelago, which is more than 800 kilometres (500 miles) north of the Norwegian mainland, but other signatory countries have rights to explore its natural resources.

A year ago, Norway expelled three Russian diplomats it identified as intelligence officers.

A man whom the Norwegian Police Security Service alleged used a false name and identity while actually working for one of Russia's intelligence services also was arrested last year. He is awaiting trial in Norway.