Ukrainian naval drones struck and disabled a tanker from Russia’s shadow fleet in the Black Sea on Wednesday as it traveled through Ukraine’s exclusive economic zone toward Novorossiysk, a Ukrainian official said.

The Dashan tanker was sailing at maximum speed with its transponders turned off and sustained critical damage during the attack, in which powerful explosions hit its stern, the official at the Security Service of Ukraine said.

The country has been carrying out attacks on Russian-linked merchant vessels in the Black Sea, heightening tensions in the region. The vessels struck by Ukraine are believed to be part of Russia's "shadow fleet," tankers Kyiv says help Moscow bypass Western sanctions by exporting oil that funds its war effort. Both ships were empty and en route to Novorossiysk, a major Russian Black Sea oil terminal.

The strike on the Dashan, which is under European Union and British sanctions and is sailing without a known flag registry, was also confirmed by three maritime security sources.

There was no immediate comment from Russia on the incident.