"The military will as of tomorrow raise its preparedness in Norway", Prime Minister Jonas Gahr Store told reporters.

"We currently have no reason to believe that Russia wants to involve Norway or any other country directly in the war, but the war in Ukraine means it is necessary for all NATO countries to be increasingly on their guard", he added.

Norway has overtaken Russia as Europe's main natural gas supplier following Moscow's invasion of Ukraine.

The Scandinavian country has already raised security around its strategic sites after mysterious drone flights were observed near its offshore oil and gas platforms and the suspected sabotage of Nord Stream's Baltic Sea pipelines.

In recent weeks, several Russians have been arrested in Norway for illegally flying drones in its airspace or violating photo restrictions in restricted areas.

Last week, Norway's counter-intelligence service also announced the arrest of a man suspected of being a Russian undercover agent, who according to experts could be a senior officer from the GRU military intelligence service.

"I must stress that nothing has happened in the last day or days that has prompted us to raise our preparedness now. It is an evolution over time which has led us to take this step", Store said.

Defence Minister Bjorn Arild Gram meanwhile said the increased military preparedness would include measures related to logistics, communications security and security at military installations.

Amid rising tensions between Russia and the West, Norway has already boosted its military budget and intelligence efforts in Northern Norway, where it shares a 198-kilometre (123-mile) border with Russia.