At least 11 crew members remain missing after a commercial ship sank in a drone attack off Bulgaria’s Black Sea coast, while five people have been rescued from the vessel, according to the latest reports on Tuesday.

Two commercial ships were struck by drones of unknown origin early Tuesday, prompting emergency rescue operations, Bulgarian Prime Minister Rumen Radev said.

The second vessel, the Maltese-flagged Chelsea 3, was hit by three drones approximately 18 nautical miles (33 kilometres) off Bulgaria’s coast at around 1:30 a.m. local time.

All 15 crew members aboard the ship — seven Ukrainians and eight Azerbaijanis — were rescued. Five received medical assistance for non-serious injuries, according to Radev.

Radev condemned the attacks as “absolutely unacceptable” and said he would seek assistance from NATO Secretary-General Mark Rutte.

Although the origin of the drones has not been established, Radev said there was no conclusive evidence identifying those responsible. He added that the outcome of the attacks benefited Russia and announced plans to summon the Russian ambassador.

The attacks have raised fresh concerns about maritime security in the Black Sea, where commercial shipping has faced growing risks amid the war between Russia and Ukraine.

Tuesday’s incident came exactly one week after drones struck two other commercial vessels in Bulgaria’s exclusive economic zone. One ship sank, while the crew of the second vessel was rescued.

In that earlier incident, Bulgarian authorities subsequently halted the search for the missing crew of the sunken ship after finding no survivors.

European Commission President Ursula von der Leyen condemned the latest attacks, warning that the Black Sea had become another front in the escalation of the war in Ukraine. She called for those responsible to be held accountable.

The latest attacks add to a series of incidents involving commercial vessels in the Black Sea, raising concerns about the safety of seafarers and the disruption of vital maritime trade routes.

Authorities have yet to publicly establish who was responsible for Tuesday’s strikes. (ILKHA)