"The situation is being treated with the utmost seriousness," NATO Secretary-General Mark Rutte said at a news conference in Luxembourg on Tuesday, according to AP News."I can assure you that we are working day and night to counter this, to prevent it and to make sure it doesn't happen again."

Although neither Russia nor von der Leyen have commented on the incident, Rutte said the jamming is part of a broader campaign of"hybrid threats," which includes actions such as cutting submarine cables, cyberattacks, and assassination attempts.

Civilian aircraft increasingly exposed in Russia's hybrid war

The plane carrying von der Leyen lost its GPS signal in Bulgarian airspace on Sunday but managed to land safely in Romania. Bulgarian authorities suspect Russia of involvement in the navigation interference, and the incident raises new questions about air safety in Europe and the growing risks posed by Moscow's hybrid actions.

"I've always hated the term hybrid, because it sounds harmless, but hybrid means exactly that: jamming commercial aircraft, with potentially disastrous effects," the NATO official explained.

Europe, as vulnerable as the eastern flank to Russian missiles

According to the NATO Secretary General, the whole of Europe is now exposed:"The threat from the Russians is growing every day. Let's not be naive: one day it may involve Luxembourg, it may reach the Netherlands. With the latest Russian missile technology, the difference between Lithuania and Madrid is 5 to 10 minutes."

Bulgarian Prime Minister Rosen Zhelyazkov said his country would not open an investigation, as"such things happen every day" and are side effects of Russia's war in Ukraine, seen across Europe.

The Associated Press has identified nearly 80 similar incidents across Europe, in a campaign of disruption attributed to Russia, described by British officials as"incredibly reckless."