A Russian missile appears likely to have entered the airspace of NATO-member Poland on Friday, a Polish general said, after an unidentified aerial object was spotted in the early morning hours amid a heavy Russian attack on Ukraine overnight.

General Maciej Klisz, operational commander of the Polish armed forces, said the object most likely spent less than three minutes in Polish airspace and went back over Ukraine.

“The entire flight path over Polish territory was being monitored,” Klisz told reporters. “At the moment, the scenario that I am recommending is that the missile left Poland’s airspace.”

Poland summoned the Russian charge d’affaires and demanded an explanation for the violation of Poland’s airspace by a missile and an immediate halt to such activities, the foreign ministry said in a statement on Friday evening.