(Bloomberg) -- Sweeping European sanctions on the purchase and transportation of Russian oil have prompted the country to transport more crude on its own tankers.

The European Union banned almost all seaborne oil imports from Russia from Dec. 5, and also joined with Group of Seven nations in capping the price at which Moscow can sell barrels. Anyone wanting to hire European ships, including the giant Greek tanker fleet, or access other vital services can only do so if they pay $60 a barrel or less for the cargoes.

Since that date European-owned tankers have taken about 30% of the cargoes shipped from Russia’s key western oil ports, down from about half before. By contrast, the share moving on Russian vessels has risen to 35%, up from 22% previously.

A shadow fleet of tankers emerged since the sanctions were signposted, with speculation the ships would be used for Russian trading. There’s also been an increase in the number of vessels whose ownership information isn’t known, suggesting some of those shadow-fleet tankers may have been deployed too.

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