A balloon entered Poland's airspace in the afternoon on June 20 from Russia's Kaliningrad Oblast, the Polish military said, adding it poses no threat.
Tensions between NATO and Russia have been mounting since the outbreak of the full-scale war in Ukraine, and cases of Russian aircraft breaching allied airspace have been a common occurrence.
In this case, Russia likely lost control of the balloon in Kaliningrad Oblast after it "broke off its tether and flew into Polish airspace," Warsaw said.
"Russian authorities previously informed us about the possibility of the object entering the area," the Polish Armed Forces Operational Command reported.
"Preliminary assessments indicate that the Russian side has lost control over one of the aerostats protecting facilities in Kaliningrad Oblast."
The Polish military said it has been monitoring the balloon. It entered the Polish airspace at around 3:30 near the border with Russia's Kaliningrad Oblast and is expected to leave at around 8 p.m. local time, the Polish military said at 7:53 p.m. local time.
Poland's Air Force regularly scrambles its fighter jets during Russia's mass attacks against western Ukraine, and there have been recorded cases of Russian missiles briefly entering Polish airspace.
In another incident on Nov. 15, 2022, a missile flew onto Polish territory during a Russian mass strike, killing two civilians. Polish investigators later concluded that it was a stray Ukrainian anti-air projectile launched to intercept the Russian attack.