Several crew members from a cargo ship that foundered in Bulgarian waters of the Black Sea remain unaccounted for following an incident attributed to a drone strike — one that Prime Minister Rumen Radev described as a violation of international law.

No claim of responsibility had emerged by Tuesday for the combined aerial and maritime drone strike roughly 110 kilometres from Byala, a town on Bulgaria's eastern coastline, while analysts and officials have noted an increase in what they describe as hybrid operations linked to the conflict in Ukraine. Industry sources noted that no comparable incident had previously been recorded within the maritime boundaries of Bulgaria's exclusive economic zone.

Radev noted that the origin of the drones — whether they were launched from Russian or Ukrainian territory — had not been established, a point relayed through a broadcast outlet regarded as reliable. Responsibility for the attack was placed on Russia by Bulgaria's top foreign affairs official. No statement addressing the episode has come from Russian officials.

According to a televised address by Radev, the assault left two vessels damaged. Rescuers brought all those on board to safety after reaching the single-operator, grain-carrying vessel, though two people among them sustained injuries. A vessel sailing under Togo's flag went down, with no details about its cargo made available. The number of people aboard had yet to be confirmed.

The incident took place approximately 140 nautical miles off the Ukrainian coastline. Efforts to locate the missing crew members got under way alongside checks for any potential environmental impact. Early assessments of the strike pointed toward a Russian origin, according to a source within maritime security circles.

Radev did not name those responsible, though he drew a connection to the conflict in Ukraine, stating that unless hostilities there were halted in time, the fighting stood to spread across a wider area and raise the prospect of broader international confrontation — a trajectory he said was already visible in the intensifying violence, the breakdown of international legal norms, and strikes against non-military vessels at sea.

Though Bulgaria shares no land boundary with either nation, its position along the Black Sea — a body of water where both Ukraine and Russia maintain notable port infrastructure — gives it considerable geopolitical weight in the region.

European Commission President Ursula von der Leyen added her voice to the condemnation, noting that merchant vessels and their crews were being targeted in attacks that had already cost lives at sea. Ukraine's Foreign Minister Andrii Sybiha posted on X that strikes against civilian shipping were producing a chain of consequences that made navigation increasingly difficult, arguing that complicating passage through those waters pushes up hazard levels, insurance premiums, and freight expenses, while also putting the steady supply of food to world markets at risk.

Two cargo vessels — the Togo-flagged ALFA WATAN and the Palau-flagged ABLE — came under attack on Tuesday within Bulgaria's exclusive economic zone, according to a statement from British maritime risk management group Vanguard.

Two fatalities were recorded aboard a vessel burning in the Black Sea beyond Romanian territorial limits, according to Romanian authorities — an incident that Ukrainian President Volodymyr Zelenskiy attributed to Russian drone activity. Maritime security firm MARISKS, in a notice directed at vessel captains and operators, flagged a pattern of unmanned aerial incidents now reaching into the exclusive economic zones of NATO members Romania and Bulgaria, territory extending beyond the waters that directly border Ukraine. No statement on that episode has come from Russian authorities.

Reports from across Europe, logged on multiple occasions after the conflict in Ukraine began in 2022, have documented unmanned aerial vehicles entering national airspace without authorisation, alongside mines observed drifting through Black Sea corridors used for trade and energy transport.