A European naval mission boarded a Russia-linked oil tanker suspected of sailing under a false flag this week, the EU’s top diplomat Kaja Kallas said Wednesday.

Personnel operating under the Mediterranean naval initiative Operation EUNAVFOR MED IRINI boarded the MV South Star on Monday for “flag verification,” Kallas wrote in a post on X.

“We’re turning up the pressure on Russia’s shadow fleet,” she said, referring to vessels with opaque ownership used to skirt Western sanctions against Russia.

The EU’s naval force mission confirmed its crew boarded the sanctioned tanker in international waters in the Mediterranean Sea.

Both Kallas and the EU published photos showing military helicopters and speedboats encircling the vessel.