The strikes targeted ships sailing under the flags of Togo and Palau, according to Bulgarian outlets BGNEWS and Nova, which reported the first attack on commercial vessels this close to the Bulgarian coast in those waters.

The ALFA WATAN, sailing under the Togo flag, sank, the reports said. There is no information on the fate of its crew, and a rescue operation is ongoing. The number of people on board has not been disclosed.

Eighteen sailors were rescued from the second vessel, the Palau-flagged ABLE, and some of them were wounded. Both ships were in Bulgaria's exclusive economic zone at the time of the attack, but not in its territorial waters.

Bulgarian Prime Minister Rumen Radev convened an emergency meeting with representatives of state institutions and announced a public statement. The office of President Iliana Yotova confirmed the attack in an electronic message without providing details. According to the Bulgarian news agency BTA, Yotova cut short a trip around the country.

Neither Russia nor Ukraine has commented on the strikes so far. It is not known who owned the drones, and there is no information on deaths or injuries.

According to Marine Traffic, the sunken vessel was heading from Egypt to Romania, while the ABLE was traveling from Romania to Istanbul.

The day before, a Turkish vessel, the Royad Mammadov, sank in the Black Sea off Romania's coast after a drone attack while carrying grain from Ukraine to Italy. Two people died and 11 crew members were rescued, according to HotNews, citing Romania's Interior Ministry. Ukrainian President Volodymyr Zelensky said the ship was attacked by two Russian drones and that Azerbaijani and Indian citizens were on board.

According to independent media reports, Russia has recently stepped up strikes on Ukrainian ports and on ships in the Black Sea heading to or from Ukraine. Moscow describes this as a response to Ukrainian strikes on Russian or Russia-linked vessels. Against that backdrop, Russian President Vladimir Putin has ruled out, for now, any agreements to halt the strikes.