Norway has begun stepping up its patrolling of oil and natural gas fields in the North Sea, after raising the level of alert for its military on Tuesday. The country shares an about 200-kilometer border with Russia.

In a news conference on Monday, Norwegian Prime Minister Jonas Gahr Store said, "We have today no reason to believe that Russia wants to involve Norway or any other country in direct warfare."

But Store also said, "The Russian attack on Ukraine has led to the most severe security situation in Europe in several decades."

Norway is the largest exporter of natural gas to Europe, where countries are trying to reduce their reliance on Russian energy.
Last month, Norwegian police arrested Russians in connection with suspicious drones flying over an energy-related facility in the country.

In September, undersea gas leaks from four places in pipelines linking Russia and Germany were confirmed, raising suspicion of sabotage.