The United States told the United Nations Security Council on Friday it would "defend every inch of NATO territory" after a suspected Russian drone incursion into Poland.

Alarms bells sounded this week in Europe after NATO jets scrambled to intercept an unprecedented Russian drone incursion in Poland. Now there is fresh unease on NATO’s eastern flank, as Russia and Belarus kick off major military drills to test the readiness of their armed forces.

The consultations at NATO headquarters were part of a regular meeting of ambassadors from the alliance's 32 member states known as the North Atlantic Council, but Polish Prime Minister Donald Tusk told Parliament that they came under Article 4 of the treaty that founded NATO in 1949 in the aftermath of World War II.

NATO Secretary-General Mark Rutte called Russia's behavior "reckless" after several drones from the country crossed into Poland, violating NATO airspace.

Poland has triggered Article 4 of the North Atlantic Treaty Organization, NATO, after the country reported 19 “breaches” of its airspace by Russian drones on Wednesday.

The incident represented the most serious spillover of the war in Ukraine for NATO, as its aircraft engaged the drones that it said came from Russia.

Europe has "nowhere near enough volume to defend itself in the event of a major and protracted war," Matthew Savill told Newsweek.

For more than three years, Ukraine has been battling Russian attack drones. On Wednesday, NATO got a taste of that fight.