Bulgaria on Tuesday summoned the Russian ambassador in Sofia after a merchant ship was sunk by a drone in the Black Sea overnight, leaving eleven crew members unaccounted for.

Drone strike raises regional security concerns

Local maritime officials said the vessel, sailing under a Bulgarian flag, was hit by an unmanned aerial system shortly after 02:00 GMT near the port of Burgas. The impact caused the hull to breach, and the ship sank within hours.

Rescue teams recovered several bodies, but eleven sailors remain missing, according to the Bulgarian coastguard. The crew were a mixed crew of Ukrainians, Bulgarians and other nationals.

sunken merchant ship in the Black Sea, rescue boats nearby

Bulgaria's diplomatic response

Foreign Minister Mariya Gospodinova told reporters that the attack "constitutes a serious breach of international law and threatens the safety of our maritime trade routes". She added that Bulgaria had formally called in the Russian ambassador to convey the government's protest.

The Russian foreign ministry, in a brief statement, expressed "deep regret over the loss of life" and said Moscow was reviewing the incident. No official claim of responsibility has been made, but Bulgarian authorities have repeatedly accused Russian forces of targeting civilian cargo vessels in the Black Sea.

Pattern of attacks on commercial shipping

DW News reported that this is the second drone strike on a merchant ship off Bulgaria's coast within a week, highlighting a growing trend of aerial assaults on commercial traffic. Analysts note that Russia has intensified the use of loitering munitions to disrupt supply lines supporting Ukraine, a tactic that spills over into neighbouring waters.

Since the start of the Ukraine war, the Black Sea has become a contested arena, with both sides deploying naval mines, anti‑ship missiles and drones. The United Nations Convention on the Law of the Sea obliges warring parties to safeguard neutral shipping, a principle that appears increasingly ignored.

Implications for regional stability

Security experts warn that repeated attacks on civilian vessels could draw Bulgaria and other NATO members deeper into the conflict. "If the pattern continues, we may see a broader escalation that pulls the alliance into direct confrontation," said Dr Lena Petrova, a senior fellow at the European Centre for Security Studies.

Neighbouring Romania and Turkey have also reported heightened naval activity, prompting NATO's maritime command to increase patrols in the southern Black Sea.

For the missing crew, families in Bulgaria and Ukraine are awaiting further information. The International Labour Organization has called for an urgent investigation and safe retrieval of survivors.

Bulgarian authorities said they will convene a special parliamentary session next week to discuss possible measures, including tighter maritime security protocols and coordination with NATO forces.

Russia's next diplomatic move remains unclear, but the incident is likely to shape discussions at the upcoming NATO summit in Brussels, where allies are expected to address the spill‑over effects of the Ukraine war.

Meanwhile, commercial operators are reviewing routing options to avoid the high‑risk zone, a shift that could impact freight costs across Europe.

Further updates are expected as rescue operations continue and diplomatic talks progress.