Bulgaria says Russia was likely behind drone attacks that struck four ships in the Black Sea over the past week, but the country’s prime minister acknowledged on Wednesday that Moscow’s responsibility could not be proved.

The latest strikes hit two commercial vessels in Bulgaria’s exclusive economic zone and adjacent waters. The Associated Press reported that one ship sank and that rescuers were still searching for 11 missing crew members, while five others had been rescued.

The Guinea-Bissau-flagged cargo ship Dignity sank after being hit by what Bulgarian officials described as a military strike. A second vessel, the Chelsea-3, was Ukrainian-owned, registered in Odesa and sailing under the Maltese flag. The details underline how the consequences of the war are reaching ships whose ownership, crews and flags cross several jurisdictions.

Prime Minister Rumen Radev told parliament that there was no obvious reason for Ukraine to attack its own ships and crews because the outcome would benefit Russia. But he also said Bulgaria could not prove Russian culpability. The Russian ambassador did not rule out the possibility that the attacks were a provocation by a third party.

That distinction is central to the story. The loss of the ships and the missing sailors are reported facts; attribution remains a claim under investigation. Treating the likely explanation as a proven one could turn a rescue and maritime-security story into an escalation narrative before investigators have established who launched the drones.

Bulgaria has asked for international assistance with the investigation and NATO support to strengthen surveillance, control systems and responses to drone attacks. President Iliana Yotova has also called for a halt to attacks on commercial and civilian infrastructure in the Black Sea.

The risk is not confined to one shipping route. Commercial operators already factor mines, missiles, drones, insurance costs and changing navigation warnings into their decisions. If attacks on merchant vessels become more frequent, vessels may be diverted, crews may face longer journeys and coastal states may be pushed into a security role they cannot perform alone.

The immediate priorities are the search for the missing sailors, a transparent investigation and reliable information about the threat. Any conclusion about responsibility must follow that evidence rather than precede it.