The Chelsea 3, a Maltese-flagged vessel owned by a Ukrainian company, was en route from Turkey to Moldova when three drones struck it 33 kilometers from the town of Byala, Radev said.
Its 15-member crew — seven Ukrainian citizens and eight Azerbaijani citizens — was evacuated. Five sailors sustained minor injuries from the drone strikes.
The second vessel sank 32 kilometers from the village of Krapets. One crew member was rescued, Radev said. The fate of the others was not reported.
"This is completely unacceptable — another attack in the immediate vicinity of Bulgarian territorial waters," Radev said in a video address. He said he has a conversation scheduled with NATO Secretary General Mark Rutte.
Ukrainian Foreign Minister Andrii Sybiha called "Russia's latest attack on merchant ships" off the Bulgarian coast a demonstration of Moscow's disregard for the lives of civilians and the safety of navigation in the Black Sea. "This is a vital channel for global food security," he said, urging partners to increase pressure on Russia.
A week earlier, drones attacked two other vessels in Bulgaria's exclusive economic zone. The Togo-flagged Alfa Watan sank about 110 kilometers off the coast, and its crew was declared missing. All 18 sailors were rescued from the Palau-flagged Able, and two were injured. At the time, Volodymyr Zelensky said Russian drones carried out the strikes and that Kyiv had not conducted operations in that area of the Black Sea.
According to Radev, Sofia does not have "weighty and unambiguous evidence to bring accusations." "Logic indicates that the result is beneficial to the Russian Federation," he added. Russian Ambassador Eleonora Mitrofanova has been summoned to Bulgaria's Foreign Ministry over the incident, the prime minister said.