NATO warned Russia on Tuesday that it would use "all necessary military and non-military tools" to defend itself as it condemned Moscow for violating Estonian airspace in "a pattern of increasingly irresponsible behaviour".

Two NATO officials, who asked for anonymity to discuss sensitive operational matters, told NBC News U.S. fighter jets were taking off for assignments somewhere in Eastern Europe.

Russian drones have reportedly been spotted in Romania, Poland, and possibly Denmark, while fighter jets were recorded over Estonia., Europe, Times Now

Since Russian aircraft violated the airspace of three NATO member countries in rapid succession, the military alliance has been deliberating how to respond.

From the moment the Russian pilots entered Estonian airspace, they were pursued by Nato’s most advanced fighter jets.

The reason is a series of increasingly brazen incursions into NATO airspace. On September 8, 21 Russian drones entered Polish territory, where some of them were shot down by an unprecedented Polish-German-Italian-Dutch military operation.

Officials say defending against drones is complex and requires affordable technology which can be quickly mass produced

Germany said Thursday it would step up its defences -- from drone warfare to outer space -- at a time of growing tensions between Russia and NATO while the Ukraine war grinds on.Defence Minister Boris Pistorius said Thursday that Germany would spend 35 billion euros ($41 billion) on outer space defence by 2030,