Ukraine’s President Volodymyr Zelensky has condemned a “horrific” Russian attack on a vessel carrying corn in the Black Sea.

The ship’s captain was killed in the strike involving two drones, Zelensky said, and another sailor was unaccounted for. Eleven crew members – nationals of Azerbaijan and India – have been rescued.

Romania said it had mounted a rescue mission after “a fire on the ship Royad Mammadov” outside the country’s territorial waters. It said two people had died.

Russia has not commented, but its defence ministry earlier said it had struck two cargo vessels. Russia has been pounding Ukrainian infrastructure in what it says is retaliation for Ukrainian attacks on Russian oil refineries and ships in the Black Sea.

Monday’s attack by Russia targeted “a civilian vessel in neutral waters carrying corn and owned by Turkey”, Volodymyr Zelensky said.

He did not give the location of the ship, but Romania’s interior ministry said it had sunk about 30 nautical miles south of its port of Sfantu Gheorghe.

“At around 11:00 (09:00 GMT), Coast Guard border police officers were informed that a fire had broken out on board a commercial vessel located within Romania’s exclusive economic zone,” the ministry said in a statement.

“Eleven crew members have been rescued. Two deceased persons have also been identified,” it added.

Ukraine’s president said he had “repeatedly proposed concrete steps to de-escalate the situation and ensure security in the Black Sea” – and other countries had made “relevant proposals” too.

“But Russia consistently chooses terror and sinking civilian vessels instead of normal maritime navigation,” Zelensky said.

“Pressure is needed to restore global food security,” he added. “And everyone who is genuinely interested in this must help.”

On Sunday, Russia’s defence ministry said it would intensify its strikes across Ukraine in response to comments made by Zelensky earlier last week, in which he said Kyiv would ramp up its attacks on Russian oil refineries.

Ukraine maintains it began attacking Russian oil infrastructure because it helped the Kremlin finance the war which began with Russia’s full-scale invasion in February 2022.

President Vladimir Putin admitted last week Kyiv had “got some results” from its refinery attacks and Russia had lost about 1% of its GDP.

The Russian leader has also intensified his rhetoric against Western allies of Ukraine – repeating a threat of even using nuclear weapons.

Western allies have faced a surge in so-called hybrid warfare incidents blamed on Russia, particularly in Poland and the Baltics in recent months.

German Chancellor Friedrich Merz said last Thursday that his country was preparing for further hybrid attacks, “including serious ones”, after a drone armed with explosives was found in August on the tarmac at Leipzig airport close to Ukrainian cargo planes.

The head of Germany’s foreign intelligence Martin Jaeger said on Monday that “Germany is in danger of becoming embroiled in a violent conflict with Russia”, which was “waging a shadow war” with the threat of attacks against targets in Germany remaining “real and imminent”.