“The secret transfer of Russian fuel cargoes between tankers at sea has been moved to new locations off the coast of Greece, after the country used naval exercises to try to block the activity in the laconic Gulf”the Bloomberg agency reported today.

About 1 million barrels of diesel, fuel oil and other petroleum products per month are transported near the islands of Lesvos and Chios in the Aegean, according to data from analysis company Vortexa.

Bloomberg adds that the area became famous only after Greece’s navy conducted exercises around the Laconian Gulf, previously the No. 1 location for the practice in Europe.

The increase in ship-to-ship transfers of Russian oil and other fuels in and around Europe has raised environmental concerns due to questions about the safety and insurance of the vessels involved.

This practice, sometimes carried out in secret with transponders turned off, hides the origin of the oil, helping to avoid sanctions while also creating another layer of separation between buyers and sellers of the cargo.

Ship-to-ship cargo transfers are still happening near the Laconic Gulf, but at a much reduced rate since Greece’s naval exercises began, Bloomberg adds.

Transports have also been taking place off the Italian port of Augusta since May, when the Greek navy began its exercises. On November 14, the exercises were extended until mid-March.