A Russian warship is reported to have fired warning shots at a small general cargo vessel in the south-western Black Sea on Sunday.

This is thought to be the first time Russia has fired on a merchant beyond Ukraine since exiting the landmark United Nations-brokered Black Sea Grain Initiative deal last month.

The 3,270-dwt Sukru Okan (built 1989) was said to have been fired upon after Russia said the ship’s captain failed to respond to a request to halt for an inspection.

Reports said Russian military personnel then boarded the Palau-flagged vessel with the help of a Ka-29 helicopter.

“To forcibly stop the vessel, warning fire was opened from automatic weapons," the Russian defence ministry said, as reported by Reuters.

“After the inspection group completed its work on board, the Sukru Okan continued on its way to the port of Izmail.”

Mykhailo Podolyak, senior advisor to Ukrainian President Volodymyr Zelenskyy said in a post on social media platform X, that the incident was a “clear violation of international law of the sea, an act of piracy and a crime against civilian vessels of a third country in the waters of other states”.

“This precedent with the attempt to introduce a ‘Letter of Marque and Reprisal’ requires clear legal fixation, identification of all persons and recognition of the fact of the crime by the international community,” he said.

“Ukraine will draw all the necessary conclusions and choose the best possible response.”

Since Russia left the Black Sea Grain Initiative in July, both Russia and Ukraine have threatened to target commercial vessels calling at each other’s ports.

Russia has said it will treat any ships approaching Ukrainian ports as potential military vessels, and their flag countries as combatants on the Ukrainian side.

Ukraine also attacked a Russian oil tanker and a warship at its Novorossiysk naval base, next door to a major grain and oil port.

Security company Diaplous Group advised shipowners to maintain the “maximum possible distance” from Russian warships and to maintain “extreme vigilance” in order to identify irregular activity in the vicinity of their own vessels.