Romania's Prime Minister called the attack on the three vessels Saturday 'unacceptable' and a 'violation of international law'. A day prior, a separate cargo-bound vessel was also struck. No injuries were reported.
Three commercial vessels were struck on Saturday evening by drones off Romania's Black Sea coast, Romanian authorities confirmed.
The drones struck the vessels near the country's Sulina canal, a key shipping route connecting the Danube river to the Black Sea and used by Ukraine to export goods.
No injuries were reported and the crews managed to extinguish the fires that broke out on board the vessels, Defence Minister Stefan Radu Oprea said.
Romanian Prime Minister Luca Niculescu called the drone attacks "unacceptable" and said it violated international law.
"They reflect the deteriorating security situation caused by Russia's ongoing war against Ukraine," he wrote on X, pledging to take necessary measures alongside its allies to strengthen security in the Black Sea.
"Romanian Ministry of Defence radars also detected aerial targets in the area," Niculescu said, adding that the Romanian Air Force had sent fighter jets on two separate occasions to investigate.
The ships that were struck included Greek-flagged chemical tanker Evia Petrol V and Saint Kitts and Nevis-flagged bulk carrier Marsol and oil products tanker Ali Najafov.
Earlier on Friday, Ukrainian media reported that another cargo vessel, the Palau-flagged Larissa 1, was hit by a drone while reportedly sailing towards Ukraine.
Russia denied targeting countries neighbouring Ukraine with drones.
Defence Minister Stefan Radu Oprea is due to meet his counterparts in Brussels next week, where the security situation in the Black Sea is expected to be discussed.
"We need the solidarity of our allies, shown through patrols with surveillance aircraft and through equipment for counter-drone warfare," Oprea said.