An oil tanker bearing the Greek flag was damaged in a suspected drone attack in the Black Sea while approaching the Russian port of Novorossiysk, authorities said. Greece’s shipping ministry said the alleged attack occurred early Saturday and caused material damage. However, the 24 crew members on board were unharmed and the vessel’s seaworthiness was not under threat.

The Maran Homer vessel, chartered by US oil giant Chevron, was hit Saturday 14 nautical miles (26 km) off Russia’s Black Sea port of Novorossiysk, AP reports. It was traveling from Thessaloniki in northern Greece to the Black Sea port and was due to sail on to Istanbul. It was reportedly struck before picking up Kazakh oil.

Greek Maritime Affairs Minister Vassilis Kikilias said Athens would lodge a “strong complaint” with the country deemed responsible, but did not give further details.

He later identified Ukraine as carrying out frequent attacks in the Black Sea, but did not placed the blame on the war-torn country.

“I consider the targeting of vessels flying the Greek flag — as well as those with Greek sailors and Greek shipping interests — to be unacceptable and extremely dangerous,” Kikilias told state-run ERT television.

Citing information from the MTI Network, Bloomberg reported that “the fleet of Greece-based Maran Tanker Management has not lifted Russian-origin oil since the start of the war in Ukraine”.

It also added “Ukraine has also been hitting Russia’s loading terminals, pipelines networks and refineries in a move to reduce fuel supplies to the front lines,” while “Russia has been relentlessly targeting Ukraine’s civil and energy infrastructure, leaving millions of people without power and heating”.

So far, no one has claimed responsibility for the attack on the Maran Homer.