Tankers are transferring about 1m barrels per month of Russian oil in the Aegean Sea off Greece.
This is according to Vortexa data cited by Bloomberg.
New hotspots have emerged after Greek naval exercises deterred transfers happening in the Laconian Gulf.
Diesel, fuel oil and other products are now being switched on vessels near the islands of Lesbos and Chios.
Concerns have been raised about the safety of the operations and the insurance cover of the ships involved.
Vessels sometimes turn off their AIS signals during transfers.
The switches can help disguise the origins of the oil on board.
Vortexa data shows the operations are still happening near the Laconian Gulf, but at lower rates.
Naval manoeuvres that began there in May have left a narrow stretch of water unaffected.
Tracking data also highlights regular transfers now happening off the Italian port of Augusta.
Greek exercises have been extended into March next year.
The government said earlier this year that it wanted to stop risky transfers of oil.
The drills have sent Russian-trading tankers into new locations in the Mediterranean and Red Sea and off West Africa.
Reuters reported in the summer that cargoes were loaded on at least seven vessels in Russia’s Black Sea ports of Taman and Tuapse in July and August for transshipment to other vessels in the northern Aegean.
LSEG data showed that four tankers carrying 123,000 tonnes of diesel and gasoil from Taman and Tuapse switched cargoes off Chios in July.
