Drones sank a cargo ship and set another ablaze off Bulgaria early Tuesday, leaving sailors missing and prompting an emergency response from the NATO member. Bulgarian authorities said the attacks involved aerial and sea drones about 70 nautical miles east of Byala.

The strikes appeared to be the first such attack on commercial shipping in Bulgaria’s exclusive economic zone. They extended the threat to merchant vessels farther into the western Black Sea, away from Ukraine’s coast.

The Togo-flagged Alfa Watan sank after suffering severe structural damage. Bulgarian sources reported Tuesday evening that its 10-member crew remained missing. The Turkish-owned ship had been sailing from Egypt toward Romania.

The Palau-flagged Able caught fire, but the Bulgarian ferry Dioscuria rescued all 18 people aboard. One sailor remained in critical condition with extensive burns, while the captain was discharged after treatment.

Prime Minister Rumen Radev said rescuers found an overturned boat, overturned life rafts and life jackets near the sunken vessel, but no people. The attacks occurred around 3 a.m., he said.

Ukrainian President Volodymyr Zelenskyy blamed Russia in his nightly address, saying Ukrainian and Bulgarian naval officials had established that Russian aerial and maritime drones carried out the attack. He said Ukrainian forces had conducted no operations in that part of the sea. Russia had not commented.

Bulgaria had not publicly confirmed that attribution. Defense Minister Dimitar Stoyanov said drone wreckage needed to be recovered to establish its origin. President Iliana Iotova called a national security council meeting for Wednesday to address maritime threats and critical infrastructure.

The strikes followed a separate drone attack a day earlier on a Turkish-owned cargo ship in the Black Sea. That vessel later sank, with two people killed and 11 rescued, Romanian authorities said. NATO declined to comment on Tuesday’s attacks and referred questions to Bulgarian officials.