Russia said on Saturday it had repelled an attempted Ukrainian drone attack on Russian “civilian transport ships” on Friday evening in the southwestern part of the Black Sea, a key artery for grain and oil exports from both countries. Civilian vessels on the Black Sea have not generally been targeted since Moscow ordered its troops into Ukraine in February 2022, but last July both sides said they would start treating ships headed to the other’s ports as potential carriers of military cargo.

In a statement posted on the Telegram messaging app, Russia’s Defence Ministry said Ukraine had attempted what it called “a terrorist attack on Russian civilian transport ships using semi-submersible naval drones”. It said Russian patrol boats and warplanes had averted the attack, destroying one Ukrainian naval drone by artillery fire and disabling the rest by electronic warfare. No Russian civilian or military vessels were damaged, it said.

Reuters could not verify the Russian account. There was no immediate comment from Ukraine. Last July, Russia refused to renew a Turkish-brokered deal providing for safe grain exports through the region and said all ships heading to Ukrainian ports would be treated as potential carriers of military cargo. A day later, Ukraine said it would adopt the same stance on ships bound for Russian and Russian-controlled Ukrainian ports.

It was not clear precisely where the attack took place. The southwestern part of the Black Sea adjoins Turkey’s Bosphorus Strait through which cargoes leaving the sea travel. Ukraine has in recent months mounted a series of drone and missile attacks on Russian military targets in the Black Sea, sinking at least one naval vessel and damaging others.