Drones struck two additional commercial vessels in Bulgaria’s Black Sea exclusive economic zone on Tuesday, marking the second such attack within a week and prompting Sofia to request expanded NATO and EU support for maritime monitoring.

Foreign Minister Velislava Petrova confirmed the incidents, stating that Bulgaria had formally asked both alliances for assistance in investigating the attacks and enhancing surveillance of its air and maritime zones.

Prime Minister Rumen Radev summoned Russia’s ambassador to discuss the strikes, noting that while no definitive attribution had been made, the pattern of incidents aligned with Russia’s strategic interests in the region.

The latest assaults targeted the Maltese-registered, Ukrainian-owned cargo ship Chelsea 3, which was hit by three drones approximately 20 nautical miles off Bulgaria’s northern coast.

All crew members were rescued by Bulgarian coast guard units, though the status of personnel from a second vessel that sank nearby remained unconfirmed.

These attacks follow a series of similar strikes against commercial shipping in the western Black Sea, including incidents involving the MV Happy Lady and the MV Swan, both of which were damaged in prior assaults attributed to unmanned aerial systems.

NATO has not issued a public statement on the recent incidents, though officials indicated that the alliance may increase aerial patrols and intelligence-sharing with member states to monitor suspicious drone activity.

The Montreux Convention, which governs naval passage through the Bosporus Strait, continues to restrict NATO’s ability to deploy warships into the Black Sea, complicating rapid response options.

European security analysts have described the campaign of targeted drone strikes as part of a broader Russian strategy of gray zone warfare — actions that fall below the threshold of armed conflict but aim to destabilize regional stability and challenge Western support for Ukraine.

While Bulgaria has not formally accused Russia of orchestrating the attacks, government officials emphasized that the incidents underscore growing vulnerabilities in civilian maritime infrastructure near NATO’s eastern flank.

Petrova reiterated that safeguarding freedom of navigation and protecting civilian crews remain central to Bulgaria’s security priorities, calling for urgent international coordination to prevent further escalation.