BRUSSELS: A group of northern European countries vowed Thursday to harden the fight against Russia’s “shadow fleet” of tankers exporting its sanctioned oil, as Turkish officials said that one of those tankers approaching the Black Sea entrance to the Bosporus Strait was hit by a naval drone.

Russia’s shadow fleet is made up of aging tankers that are bought used, often by nontransparent entities with addresses in countries that are not sanctioning Russia. Moscow needs the vessels to dodge Western sanctions and sell the oil and petroleum products that largely finance its more than 4-year invasion of Ukraine.

British Prime Minister Keir Starmer said at a meeting with allies in Finland that “we should go after the shadow fleet even harder.”

Speaking with other members of the Joint Expeditionary Force, a 10-country group that has been tracking the vessels, Starmer said the British military will now be able to board shadow fleet tankers when they transit UK waters, joining several other allies in doing so.

“Together, we must close off critical sea routes to this vital trade, to keep up the pressure on (Russian President Vladimir) Putin and to help change the narrative of this war” in Ukraine, Starmer said.