SOFIA, Bulgaria — Three maritime drones struck a container ship sailing in the Black Sea off the coast of Bulgaria on Wednesday, the country’s defense minister said, the latest in a string of such incidents on NATO’s eastern flank.

The attack on the Liberian-flagged container ship, the Contship Jet, occurred a little before 1 p.m. local time about 21 nautical miles southeast of the coastal town of Shabla, near Cape Kaliakra in northeastern Bulgaria, Defense Minister Dimitar Stoyanov told reporters.

The crew evacuated the vessel, and there were no immediate reports of casualties, according to Bulgarian state news agency BTA.

The incident took place as defense ministers from Bulgaria, Romania and Turkey were meeting in the Bulgarian capital, Sofia, for trilateral talks focused on security in the Black Sea region.

A series of drone attacks have occurred this month off the coasts of NATO members Romania and Bulgaria, leading some members of the alliance to wonder if Russian President Vladimir Putin is seeking to test their support for Ukraine in its war against Moscow’s full-scale invasion.

Russia has not taken responsibility for the attacks, but increasingly, suspicion has fallen on Moscow. Bulgarian Prime Minister Rumen Radev told his country’s Parliament earlier this month that “the logic points in that direction … The problem is that we cannot prove it.”On Oct. 15, NATO Secretary-General Mark Rutte said in a post on X that NATO had “strengthened our posture along the eastern flank including with increasing counter-drone capabilities” in the face of increasingly frequent strikes on commercial vessels.

The attacks in Bulgaria and Romania’s exclusive economic zones threaten a global shipping route and have left two people dead, with at least 25 still missing.

Throughout the war, Russia has repeatedly bombarded Ukraine’s Black Sea and Danube river ports, leaving Kyiv increasingly reliant on alternative routes to get its grain exports to markets in Africa and the Middle East. Russian drones have repeatedly violated Romanian airspace near some of Ukraine’s Danube ports.

In early October, two commercial ships were attacked in Bulgaria’s exclusive economic zone, and a week later, the Guinea-Bissau-flagged HS Dignity sank after being struck about 17 nautical miles east of Shabla while the Malta-flagged Chelsea 3 was damaged in a separate attack about 17 nautical miles east of Byala, according to reports at the time.

On Oct. 23, a foreign-flagged cargo ship capsized and sank in the Black Sea following a suspected drone strike about 13 nautical miles off the Romanian port city of Constanta.