Seven of 12 crew members are missing after a drone attack left a chemical tanker ablaze off Romania's coast on Thursday morning, naval authorities say.
The San Marino-flagged Wine Trader was 13 nautical miles (24km) east of the mouth of the River Danube at Sulina, when it reported blasts and a fire.
Romanian President Nicușor Dan confirmed that the Wine Trader and another chemical tanker in the area, the Yara J, had both been struck by drones - the Yara J on Wednesday.
The Wine Trader was empty of cargo at the time.
Moscow said two cargo ships with military cargo heading to Ukraine's Odesa port had been hit. It did not name the vessels.
Overnight, a swarm of Russian drones was detected not far from the scene, near Ukraine's Snake Island.
The west coast of the Black Sea has recently seen a spate of drone attacks.
On Tuesday, two merchant ships were struck by drones further south along the coast of Bulgaria, Romania's neighbour, and one of the vessels sank, leaving 11 crew members missing.
Bulgaria said it suspected Russia was behind that attack, summoning the country's envoy.
A search and rescue operation for the missing members of the Wine Trader continues, Romania's authorities have said. Two Black Hawk helicopters and two rescue boats have been deployed.
The Romanian interior ministry has released a video showing one of the helicopters hovering above the vessel.
The priority is now to reach the four crew members confirmed to be alive, while ensuring the safety of rescue teams with very high waves reported in the area.
The Wine Trader tanker, which was sailing from Tunisia to Romania, reported several explosions on board at about 07:00 (05:00 GMT).
Romanian media cited crews on nearby ships as saying the Wine Trader had been hit by two drones.
The leaders of Romania and Bulgaria are due to discuss shortly whether Article 4 of the Nato treaty should be invoked.
This allows any member of the military alliance to request consultations with its allies if it believes its territorial integrity or security is threatened.
The Romanian president said: "We want to have all the information about what happened, but there will be a response from the Romanian state."
Dan is due to meet Nato Secretary General Mark Rutte in Brussels alongside Bulgarian Prime Minister Rumen Radev to discuss growing security threats in the Black Sea region.
The Romanian president said discussions would focus on operational requirements, including additional equipment to protect shipping in the area.
Ukraine has directly blamed Russia for earlier attacks on civilian vessels in the western side of the Black Sea - a key route for Ukrainian exports and imports.
On Tuesday, European Commission President Ursula von der Leyen spoke of the Black Sea becoming "another front of escalation of the Russian war in Ukraine. This is unacceptable".
Russia's military has recently intensified its strikes on vessels in the area, as part of its war against Ukraine.
A fire broke out on the Comoros-flagged Yara J late on Wednesday after being struck by a drone, but its crew - who are all reportedly safe - were able to douse the flames themselves.
Last week, another two ships were struck off Bulgaria, and on the same day Ukraine hit an oil tanker in the Russian Black Sea port of Sochi.
Moscow 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 attacked.
Both Russia and Ukraine are major grain-exporting countries and Turkey has called on both countries to halt attacks in the Black Sea.
Moscow has repeatedly rejected calls by the US and Europe for a naval ceasefire in the Black Sea, blaming Ukraine for attacking Russian merchant ships in the area.
Russian President Vladimir Putin launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls about 20% of Ukrainian territory.
Source: BBC
--Agencies
