"NATO is launching [Operation] Eastern Sentry to further strengthen our positions on the eastern flank," Rite said at a joint press conference with NATO Supreme Allied Commander Europe, US General Alex Grinkevich.

He added that the operation would be expanded in the coming days and would involve resources from Denmark, France, Britain and Germany.

"Along with more traditional military capabilities, this effort will also include elements designed to address specific challenges associated with the use of drones," Rite said.

"Moving forward, integrated and multi-tiered air defense - both air- and land-based - will be very important," said Grinkevich.

"We continue to assess the incidents that occurred on Wednesday, and regardless of whether Russia's actions were intentional or not, Russia violated NATO airspace," Rite said of the entry of 19 Russian drones into Polish airspace.

"Whether it was intentional or unintentional, it is dangerous and unacceptable," the alliance leader stressed.

Rite noted that Wednesday's incident was"the largest concentration of violations of NATO airspace," but that it was not an isolated incident, as other airspace violations occurred in Romania, Estonia, Latvia and Lithuania.

There are indications that the violation of Polish airspace was not accidental, according to some European politicians.

However, US President Donald Trump suggested that the drones' arrival may have been accidental, which Poland categorically denies.