Brussels, Dec 1 (IANS/TASS): NATO has had to scramble air defences around 400 times this year in response to “increased” Russian air activity, NATO Secretary-General Jens Stoltenberg said Monday.

“Russia's air activity over the past year increased 50 percent, compared with 2013,” Stoltenberg said, ahead of a meeting of the NATO foreign ministers in Brussels Dec 2-3.

The NATO chief acknowledged that training flights of Russian military planes in the international airspace are not usually considered to violate the international norms.

Stoltenberg urged Moscow to conduct military air activities more transparently, saying that the Russian planes have not been turning on their transponders and have also not been communicating with civilian air traffic controllers and not unveiling their air flight plans.

The Russian defence ministry, however, stresses that the country's air force has been conducting its training flights in the international airspace “in full compliance with the existing international norms and practices”.