Meanwhile, Ukraine continues to strike Russia’s oil refineries and export ports, while Moscow keeps up its bombardment of Ukraine’s gas and power infrastructure. The attacks show no sign of easing while a breakthrough in the US-led peace plan remains elusive.

At least three oil tankers have been hit by explosions in what appears to be a stepped up unilateral effort by Ukraine to sink Russia's sanctions-dodging oil sales.

The G7’s proposed plan to bar tankers from hauling Russian oil hinges on whether governments will ratchet up punishments on those skirting sanctions.

Bulgarian maritime authorities on Saturday launched efforts to evacuate the crew of the oil tanker Kairos stranded off the Black Sea port of Ahtopol and believed to be part of the “ shadow fleet ” used by Russia to evade international sanctions linked to its war in Ukraine.