The investigation by public broadcaster NRK, as part of a wider project with Nordic public broadcasters Danmarks Radion (DR) Sveriges Television (SVT) and Finnish Yle, used open traffic shipping data to track how Russian boats are used for espionage in the Nordics.

The boats were tracked near key infrastructure such as oil and gas fields and travelling towards military exercises and training areas and in the vicinity of American nuclear submarines.

NRK reports that police in Kirkenes, near Norway’s border with Russia, had also discovered a hidden Soviet radio hidden behind a locked door on one fishing vessel it stopped in a routine papers check.

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Nils Andreas Stensønes, a former navy chief and Head of the Norwegian Intelligence Service, told NRK that it was difficult to ascertain an overview of how many boats may be carrying out intelligence operations in Norwegian waters.

“We identify individual cases and the likelihood of individual vessels carrying out intelligence, but the specific scope is actually quite difficult to have an overview of,” he said.

“Russia is interested in Norwegian technology. And to some extent, you can get some insight into that via maritime activity,” he added.

Last week, Norway expelled 15 Russian embassy officials who it said were carrying out espionage activities in the country.

Åse Gilje Østensen, an associate professor from the Norwegian Naval Academy, said that the boats used to carry out intelligence activities likely had no choice but to do so.

“In a purely physical sense, civilian vessels will certainly be used for other things. But Russia is an authoritarian regime, and if the Kremlin asks you to carry out a mission, you really have little choice whether to carry it out or not,” Østensen said.