Russia in July halted participation in the Black Sea grain deal that allowed Ukraine to export agricultural produce via the Black Sea and Moscow cautioned that it deemed all ships heading to Ukrainian waters to be potentially carrying weapons.
Russia said in a statement that its Vasily Bykov patrol ship had fired automatic weapons on the Palau-flagged Sukru Okan vessel on Sunday after the ship's captain failed to respond to a request to halt for an inspection.
Russia said the vessel was making its way towards the Ukrainian port of Izmail. Refinitiv shipping data showed the ship was currently near the coast of Bulgaria and heading towards the Romanian port of Sulina.
"To forcibly stop the vessel, warning fire was opened from automatic weapons," the Russian defence ministry said.
The Russian military boarded the vessel with the help of a Ka-29 helicopter, the ministry said.
"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.
A spokesman for Ukraine's defence ministry said officials had no details about the incident yet but that it was "clearly another hostile act" by Russia.
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.
In Ukraine's southern region of Kherson, Russian shelling killed seven people on Sunday, including a 23-day-old infant, prompting local officials to declare Monday a day of mourning.
Kyiv reclaimed part of Kherson from Russian occupation last November but Kremlin troops have continued shelling the regional capital and areas around it from across the Dnipro River.
A couple, their 23-day-old child and another man were killed in the village of Shyroka Balka, Interior Minister Ihor Klymenko said. The couple's 12-year-old son was critically wounded and died in hospital, he added.
Two people, including the pastor of a church, were killed in the neighbouring village of Stanislav, according to Governor Oleksandr Prokudin.
Three people each in Kherson city and the town of Beryslav were wounded, according to the interior ministry, and casualties were also reported in four other settlements across the region.
