Eight of 12 crew members are missing after a tanker caught fire off Romania’s coast, naval authorities say, and there are reports of explosions on board.

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 on Thursday morning.

The west coast of the Black Sea has recenty seen a spate of drone attacks, and reports from nearby ships say the tanker was hit by two drones. Russian drones were detected overnight not far from the scene – near Ukraine’s Snake Island.

Russia said two cargo ships with military cargo heading to Ukraine’s Odesa port were hit during the sea crossing. It did not name the vessels.

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. Bulgaria said it suspected Russia was behind that attack, summoning the country’s envoy.