The Polish foreign ministry said in a statement that Russian President Vladimir Putin's "reckless actions demonstrate a complete disregard for international law and European security."
It added that the incident "is yet another reminder that Russian aggression directly threatens NATO territory and population."
Romania's defence ministry said earlier on Friday that a Russian drone entered Romanian airspace and crashed onto the roof of an apartment building in Galați, sparking a fire.
Two people suffered minor injuries, according to preliminary reports.
The incident occurred amid a Russian drone attack on Ukraine’s southern Odesa region. Ukraine's air force reported detecting 16 Russian-made Shahed drones heading toward the Danube port of Reni, located across the river from Romania and roughly 20 kilometers from Galați.
NATO accused Moscow of reckless behaviour and pledged to "defend every inch of Allied territory" .
European Commission President Ursula von der Leyen said Russia had "crossed yet another line" after one of its drones struck a densely populated area in NATO and European Union member Romania, injuring civilians during an overnight attack on neighbouring Ukraine.
"We stand in full solidarity with Romania and its people," von der Leyen said in a post on X.
"As we continue strengthening our security and deterrence, especially on our eastern border, we will keep increasing the pressure on Russia," she added.
According to Romania’s defence ministry, cited by the BBC, fragments of Russian drones have fallen on Romanian territory 47 times over the past four years.
Friday's incident was reportedly the first in which Romanian citizens were injured.
Romania, like Poland, is a member of NATO and has repeatedly reported incursions by drone debris linked to Russia’s war against Ukraine.
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Source: TVP Info, IAR, PAP, Reuters