The violation constitutes "a new challenge to regional security and stability in the Black Sea area", writes the EU and NATO country's foreign ministry in a statement, according to AFP.
The incident occurred just a few days after several Russian drones violated Polish airspace on Wednesday night. After the incident, NATO has stated that it will strengthen its presence in Eastern Europe.
Poland's foreign minister says on Sunday that the violation in Poland was a way for the Kremlin to, with cautious means, test NATO's readiness.
Interestingly, they were all (the drones) unarmed, which to me seems like Russia wanted to test us without risking starting a war, says Radoslaw Sikorski to The Guardian.
Russia has denied violating Polish airspace.
