NATO jets have intercepted Russian aircraft more than 400 times near the military alliance's European airspace this year, a 50-per-cent increase from 2013, Secretary General Jens Stoltenberg says, according to dpa. "In the Baltic Sea, in the Norwegian Sea, in the Black Sea, in the airspace surrounding NATO, we have seen increased Russian military air activity," he said during a visit to Estonia. "It's a pattern which reminds us of the way they conducted these kinds of military air activities back in the time of the Cold War." "They are not filing their flight plans, they are not turning on the transponders and they are not communicating with civilian air traffic control," he added. "The flights are unjustified and they are posing a risk [for] normal air traffic." Most of the flights are conducted in international airspace, with only "a very limited number" of NATO airspace violations, Stoltenberg said. The alliance has also stepped up its presence, deploying five times more jets on its eastern front since the beginning of 2014.