"After the inspection group completed its work on board, the Sukru Okan continued on its way to the port of Izmail," the defence ministry said.

A Turkish defence ministry official said he had heard an incident had taken place involving a ship heading for Romania, and that Ankara was looking into it.

Firing on a merchant vessel will ratchet up already acute concerns among shipowners, insurers and commodity traders about the potential dangers of getting ensnared in the Black Sea - the main route that both Ukraine and Russia use to get their agricultural produce to market.

Since Russia left the Black Sea grain deal, both Moscow and Kyiv have issued warnings and carried out attacks that have sent jitters through global commodity, oil and shipping markets.

Russia dismisses that interpretation and says the West failed to implement a parallel agreement easing rules for its own food and fertiliser exports.