Poland’s State Security Service said on Monday that a drone was “neutralized” after it flew over key government sites, including Belweder Palace, the official Warsaw residence of President Karol Nawrocki. Prime Minister Donald Tusk reported on social media that two Belarusian citizens were detained while police investigate the incident. Tusk did not share further details.

The security scare follows a September 10 incident when some 20 Russian drones entered Polish airspace. Polish and NATO fighter jets scrambled and shot down several of the unmanned aircraft, marking the first time such a clash occurred over NATO territory. The event triggered NATO’s “Operation Eastern Sentinel,” aimed at tightening defense on the alliance’s eastern flank.

Poland fully closed its border with Belarus on September 12, citing provocations by the governments in Minsk and Moscow. The move overlaps with joint Russian-Belarusian exercises, dubbed “Zapad-2025,” underway in Belarus through September 16.