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Drones struck two ships off Bulgaria's Black Sea coast on Tuesday, October 13, sinking the cargo ship HS Dignity, Al Jazeera reports. Five crew members were rescued and 11 remain missing.

HS Dignity, a Guinea-Bissau-flagged vessel, sank about 31 kilometers east of the village of Krapets, near the Romanian border, according to Helsinki Times. A search and rescue operation is continuing.

The second ship, Chelsea 3, was hit by three drones about 33 kilometers off the Bulgarian coast. The vessel is Ukrainian-owned and sails under a Maltese flag. It was damaged but did not sink.

All 15 crew on Chelsea 3 were rescued. Seven are Ukrainian and eight are Azerbaijani. Five received minor medical treatment, and the crew were taken to the port of Varna.

Bulgarian Prime Minister Rumen Radev called the attacks "absolutely unacceptable" and said they happened in the immediate vicinity of Bulgarian territorial waters. He said there is no conclusive evidence of who was responsible, though the outcome appears to benefit Russia.

Bulgaria summoned Russian Ambassador Eleonora Mitrofanova. She said she had received no information from Russia's Defence Ministry about attacks on commercial vessels. She suggested that a third party may have staged the incidents as a provocation.

European Commission President Ursula von der Leyen said the Black Sea has become another front of escalation in Russia's war in Ukraine. NATO Secretary General Mark Rutte said the alliance will keep monitoring the Black Sea and could adjust its presence on the eastern flank as needed. Ukrainian Foreign Minister Andrii Sybiha accused Moscow of targeting civilian shipping.

Early reports of the crew numbers varied, and the figures above reflect the latest counts published by Al Jazeera and Helsinki Times.

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