Romania on Wednesday was probing a possible fresh drone attack on a tanker off its Black Sea coast.
Suspected Russian drones have hit several ships off Romania and neighbouring Bulgaria since last week in the latest spillover from the Ukraine war in the Black Sea.
Romanian rescuers rushed to help the Comoros Islands-flagged Yara J late Wednesday off Sulina near the border with Ukraine, a statement said.
Defence Minister Radu Miruta said the ship's crew managed to douse a fire themselves.
"Whether it was struck by a drone or not, an investigation is currently underway," he told the Digi24 television channel.
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"This is a matter of significant gravity, given that such incidents are occurring in Romanian territorial waters," he said.
The VesselFinder tracking website identified the Yara J as a chemical/oil products tanker.
Miruta said the vessel, docked off Sulina for "several days", was empty.
The defence ministry in a press release earlier said it had scrambled two F-18 jets after "detecting a group of air targets off the Black Sea".