Polish Prime Minister Donald Tusk said on Wednesday that the EU member had invoked NATO’s Article 4 for urgent talks after Russian drones violated its airspace during a major attack on Ukraine. Polish forces downed at least three drones during the violations, Warsaw claimed.

“The allied consultations I am referring to have now taken the form of a formal request to invoke Article 4 of the North Atlantic Treaty,” Tusk told parliament.

Article 4 of the North Atlantic Treaty states that NATO member nations will consult together whenever the territorial integrity, political independence, or security of any member is threatened — even if there isn’t a direct armed attack by a potential enemy state.

Earlier, Tusk confirmed at least 19 airspace violations by Russian air assets, and the downing of three Russian drones.

Andrei Ordash, Russia’s temporary charge d’affaires in Poland, told RIA Novosti that Warsaw was yet to present evidence that the drones shot down overnight had come from Russia.