London ? British and Norwegian jets intercepted Russian military aircraft on Friday after they breached NATO airspace near the U.K. and Finland, defense officials said.

Finland’s prime minister demanded an explanation from Moscow. Interception of Russian warplanes in NATO patrolled-airspace has become increasingly common since the Kremlin ordered strategic bombers to carry out long-range missions for the first time since the breakup of the Soviet Union.

Russia said it had set up a commission to investigate the Finnish claims, but an official insisted the aircraft had flown over neutral territory.

British fighter jets intercepted two Russian long-range bombers flying in NATO airspace and shadowed them until they charged course, Britain’s defense ministry said, without revealing precisely where the incursion took place. The two Tu-160 “Blackjack” bombers were initially intercepted by Norwegian F16s, defense officials said.