In its annual national risk assessment report, the intelligence service said that in repeated incidents since 2017, GPS signals have been blocked from Russian territory in Norwegian regions near the border with Russia.

The jamming events have often coincided with military exercises on Norwegian soil, such as the NATO Trident Juncture manoeuvres last autumn and the mid-January deployment of British attack helicopters in Norway for training in Arctic conditions.

"This is not only a new challenge for Norwegian and Allied training operations," the head of the intelligence unit, Morten Haga Lunde, said as he presented the report.

"Jamming is also a threat to, among others, civilian air traffic and police and health operations in peacetime."

Norway has on several occasions raised the issue with Russian authorities, and is cooperating with other Nordic countries to gather as much information as possible, Defence Minister Frank Bakke-Jensen said.

"It's important... to say clearly that this is unacceptable," he told television channel TV2 Nyhetskanalen.

In November, neighbouring Finland summoned Russia's ambassador to Helsinki to answer to accusations that Moscow had disrupted geopositioning signals on its territory during the Trident Juncture exercises.

Moscow has rejected the allegations as baseless.