European Union forces boarded an oil tanker suspected of belonging to Russia’s sanctions-busting shadow fleet as the bloc’s foreign policy chief pledged to cut off illegal oil sales funding Moscow’s aggression in Ukraine.

EUNAVFOR MED IRINI forces boarded on Sunday the oil tanker MV SUN in the Mediterranean. It is suspected of sailing under false flag, said Kaja Kallas, the EU High Representative for Foreign Affairs and Security Policy.

“This is the sixth suspected shadow fleet vessel boarded by our EU operations in recent months,” Kallas said on X.

Russia has used shadow fleet vessels to evade sanctions on its critical oil exports. The ships tend to be older, posing security risks, and have their links to Moscow hidden, often through shell companies.

“Illegal oil sales from shadow fleet ships are a critical lifeline for Russia’s war in Ukraine,” said Kallas, “and we’ll continue to cut them off.”

Newsweek has contacted the Kremlin for comment.

This is a developing story; updates to follow.