ATHENS (Reuters) - The Greek navy this week extended an advisory effectively banning ship traffic off the coast of the southeastern Peloponnese and further, in a bid to deter ship-to-ship transfers of Russian oil off Greece, three sources said.

Greece, over the past months, has been issuing and extending such advisories for military exercises off the Laconian Gulf and even further, off the island of Kithira, urging merchant and other vessels to avoid the area.

The latest advisory was extended until Sept. 15, 2024.

"It is obviously effective in preventing transfers of shipments that should not be transferred," a key reason for its extension, one of the sources said.

Following Russia's invasion of Ukraine in 2022, international sanctions have made trading Russian crude and oil products difficult, prompting traders to seek loopholes to export them, including offshore ship-to-ship transfers.

Waters around Greece's southern coast and the Laconian Gulf have recently been meeting points for transfers from tankers carrying Russian oil onto other vessels.

Greek officials have in the past said Greek authorities cannot inspect vessels that carry a foreign flag in international waters and such naval advisories help rein in offshore ship-to-ship transfers.

(Reporting by Renee Maltezou; Editing by Bernadette Baum)

By Renee Maltezou