The explosion was likely caused by Ukrainian air defence, NATO says, emphasising that Russia bears the "ultimate responsibility" for the incident that killed two people.
An explosion in an eastern Polish village that killed two people this week showed "how close this war is coming to NATO's borders," according to the German Marshall Fund's Warsaw office director.
Michal Baranowski told Euronews that the explosion showed that the Ukraine war is "dangerously and uncomfortably close" to NATO countries.
"This missile would not have hit and would not kill two Polish citizens if Russia was not waging the war in Ukraine," the senior fellow and director of the German Marshall Fund's Warsaw Office added.
Both Polish and NATO officials have said that the preliminary investigation into the incident suggests the deadly explosion was caused by Ukrainian air defence against Russian cruise missiles.
"Let me be clear. This is not Ukraine’s fault. Russia bears ultimate responsibility, as it continues its illegal war against Ukraine," said NATO Secretary General Jens Stoltenberg on Wednesday.
Baranowski told Euronews that air defence systems use radar to pick up on incoming missiles to intercept them, but that "there is obviously a long way that debris from such an incident could fall."
He added that there are air defence systems in Poland in the southeastern city of Rzeszów.
Baranowski described the atmosphere in Poland as "tense" with "a clear sense of uncertainty and of danger" when the event happened.
"To really make sure that such an incident does not happen again, that a stray missile does not fall in NATO territory is to make sure that there are no Russian missiles flying in Ukraine and that Ukraine is able to more effectively defend itself, both when it comes to air and also land," he added.