Sweden’s navy says Russia is conducting a military-style operation in Baltic waters to protect its sanctioned shadow tanker fleet. The service reports Russian personnel in uniform, and possibly armed, on board some of the oil tankers used to move Russian crude outside Western sanctions.

Naval operations chief Marko Petkovic told local media that the navy has both observations and information indicating that certain shadow-fleet vessels are carrying Russian uniformed personnel.

He said the pattern of activity points to a more lasting Russian naval presence on key routes in the Baltic and the Gulf of Finland, with warships patrolling and providing cover for ageing tankers involved in sanction-evading trades. Sweden’s statement represents the first time a NATO navy has officially acknowledged that military personnel are embarked on shadow-fleet vessels passing through the Baltic.

Data from S&P Global Market Intelligence indicate that Russia’s shadow fleet now makes up about 17% of the world’s operational tanker fleet, roughly one in every six tankers in service. Broker BRS reports that the so-called “grey” VLCC fleet has expanded from 10% to 18% of the global VLCC fleet, while the grey Suezmax fleet has increased this year from 16% of the global Suezmax fleet to 19% of the global Suezmax fleet.