The incident came after Russia launched a large-scale missile and drone attack on Ukraine, which claimed at least three lives.

Polish and allied aircraft were also scrambled owing to the increased threat posed by the aerial actitivity.

“One of the objects flew into Polish territory,” General Maciej Klisz, operational commander of the Armed Forces, said on Monday. “The object was confirmed by radio-location by at least three radar stations. I had full control, and I was ready to shoot it down. I was also in contact with the Minister of Defense Władysław Kosiniak-Kamysz.”

The object crossed the border at about 6:43 am near the Ukrainian city of Chervonohrad. It disappeared after travelling about 25 km. The Armed Forces stressed that it was probably not a rocket, and that a search was underway.