Seven of the twelve crew members aboard the San Marino-flagged chemical tanker Wine Trader are missing after the vessel was struck by drones off Romania's Black Sea coast on Thursday morning.

The Wine Trader, sailing from Tunisia to Romania, reported several explosions and a fire at around 07:00 local time (05:00 GMT), when it was approximately 13 nautical miles east of the mouth of the River Danube at Sulina. Five crew members were confirmed safe. A search and rescue operation involving two Black Hawk helicopters and two rescue boats has been deployed. Rescue teams are operating in difficult conditions, with very high waves reported in the area.

Romanian President Nicusor Dan confirmed that both the Wine Trader and a second chemical tanker, the Comoros-flagged Yara J, had been struck by drones. The Yara J was hit late on Wednesday just inside Romanian waters. Its crew managed to extinguish the fire themselves and all are reported safe.

Romanian media cited crews on nearby vessels as saying the Wine Trader had been hit by two drones. A NATO military source said the drones that struck both tankers were of Russian origin. "The drones that caused the fires on board two tankers inside Romanian territorial waters were of Russian origin," the source said. Romanian Defence Minister Radu Miruta said an investigation was underway, adding: "This is a matter of significant gravity, given that such incidents are occurring in Romanian territorial waters."

Dan said he would not explicitly attribute responsibility, but described the situation as deeply serious. "Commercial ships are being attacked and sunk," he wrote on social media. "Seafarers killed, injured and missing very close to the shores of Romania and Bulgaria. This is unacceptable and it has to stop. Lives, global trade, and critical infrastructure are at stake."

Moscow said two cargo ships carrying military cargo bound for Ukraine's Odesa port had been hit, without naming the vessels. Overnight, a swarm of Russian drones was detected near Ukraine's Snake Island, close to the scene of the attack. The Wine Trader was empty of cargo at the time of the strike.

Dan met NATO Secretary General Mark Rutte and Bulgarian Prime Minister Rumen Radev in Brussels on Thursday, where they agreed to strengthen defences in the Black Sea. Rutte said NATO would "continue to work closely with our allies in the Black Sea, adjusting our deterrence and defence posture as needed." A NATO official said the matter would be discussed at a meeting of the North Atlantic Council the following week.

The leaders of Romania and Bulgaria are also considering whether to invoke Article 4 of the NATO treaty, which allows any member state to request consultations with allies if it believes its territorial integrity or security is threatened. Dan said: "We want to have all the information about what happened, but there will be a response from the Romanian state."

The attacks are part of a broader pattern of drone strikes on commercial shipping in the western Black Sea. In the past ten days, at least five other cargo ships have been struck off the coasts of Romania and Bulgaria. On Tuesday, two merchant vessels were hit by drones off the Bulgarian coast. One of them, the HS Dignity, a cargo ship sailing under a Guinea-Bissau flag, sank, leaving 11 crew members missing. On the second vessel, the Ukrainian-operated Chelsea 3 sailing under a Maltese flag, all 15 crew members were evacuated, with five treated for minor injuries. The crew reported the ship's deck and hull were struck by three aerial drones. According to reports, at least 23 sailors have been reported missing or killed in attacks on commercial shipping near the Bulgarian and Romanian coasts over the past ten days.

Bulgaria summoned the Russian ambassador following the Tuesday attack. Radev said after arriving in Brussels: "The results of this attack favour Russia. However, we don't have any solid evidence that the drones are Russian."

A draft EU summit declaration states that attacks against civilian shipping, including "member state-flagged vessels, such as the recent attacks in Bulgaria's and Romania's exclusive economic zones in the Black Sea, are unacceptable and constitute a serious violation of international and maritime law." Radev said the EU would also discuss a proposed moratorium on attacks on civilian ships in the Black Sea.

Ukraine has blamed Russia for the attacks on civilian vessels in the western Black Sea, a key route for Ukrainian grain, sunflower oil and other exports. Russia says it is targeting ships delivering weapons and dual-use cargo to Ukrainian ports. Kyiv and its European allies say merchant vessels carrying grain and other civilian cargo are being struck. Moscow has repeatedly rejected calls for a naval ceasefire in the Black Sea, blaming Ukraine for attacking Russian merchant ships. Russia launched its full-scale invasion of Ukraine in 2022 and currently controls approximately 20 percent of Ukrainian territory.