OSLO, April 14 — Norway's intelligence service said on Friday the expulsion of 15 Russian embassy employees suspected of being "intelligence officers", had "significantly reduced" the risk of Russian espionage but not removed it.

The Nordic country announced on Thursday that it had declared 15 Russian diplomats — about a third of staff at the embassy in Oslo — "personae non gratae" because they had been "engaging in activities that are not compatible with their diplomatic status".

The decision further strained relations between Oslo and Moscow, which have deteriorated in the wake of Russia's invasion of Ukraine.

"The risk of espionage from Russia has not disappeared but it has been significantly reduced," Inger Haugland, head of counter-intelligence at the Norwegian Police Security Service (PST), told a press briefing on Friday.

The people expelled, she explained, were "specialists in different fields".

These included recruitment of intelligence sources, wiretapping and technical espionage, and acquisition of technology, she said.

Haugland gave an example of a suspected intelligence officer who had tried, on behalf of Russian military intelligence (GRU), to acquire "advanced underwater technologies".

While Russian espionage activities under diplomatic cover had been compromised, other channels remained vulnerable, according to PST.

Haugland gave the examples of visiting spies, sleeper agents, civilian intelligence-gathering vessels and cyber espionage.

"The risk of espionage has changed because of Russia's invasion of Ukraine," Haugland noted.

"Russia has more to gain and less to lose from conducting espionage activities in Europe and Norway," she added.

According to PST, the Scandinavian country is of particular interest to Moscow for its arms industry and its energy sector. Sweden has delivered arms to Ukraine and is now the largest supplier of natural gas to Europe.

Moscow has vowed to respond to the expulsion of 15 employees.

"This is another extremely unfriendly step, which will be followed with a response measure," Russian embassy spokesman Timur Chekanov told AFP in an email. — AFP