Polish expert Marcin Zaborowski says NATO's stance on Black Sea security is not strong enough. He warned that drones are increasingly a threat to civilian ships.

Zaborowski was commenting on an attack in the Black Sea for which only Ukraine blames Russia. Bulgaria, Romania and Turkey have not blamed Moscow, he added.

Until it is clear who is behind the attack, NATO has few ways to respond directly, the expert said.

Zaborowski compared the Black Sea with the Baltic, where allies have stepped up sea patrols and surveillance. "In the Black Sea we have nothing like that right now. We have to admit that NATO's overall position in the Black Sea is not particularly strong," he told Bulgarian National Radio.