Greece says Turkish plans to map sea encroach on its territory

By Michele Kambas

ATHENS (Reuters) - Greece accused Turkey on Tuesday of attempting to encroach on its continental shelf in a serious escalation of tensions between the two NATO allies at odds over a range of issues.

Turkey and Greece are at loggerheads over overlapping claims for hydrocarbon resources, brought into sharper focus by attempts of EU member Cyprus to also explore for natural gas in the Eastern Mediterranean amid strong Turkish objections.

An advisory known as a Navtex was issued by Turkey's navy on Tuesday for seismic surveys in an area of sea between Cyprus and Crete. The advisory is in effect until Aug. 20.

Seismic surveys are part of preparatory work for potential hydrocarbons exploration. The Greek foreign ministry said the advisory covered part of the Greek continental shelf.

"We call on Turkey to immediately cease these illegal actions which violate our sovereign rights and undermine peace and security in the area," it said in a statement.

A protest had been lodged with the Turkish foreign ministry while the United Nations, the five permanent members of the U.N. Security Council, NATO and the European Union had been informed.

There was no immediate comment from Turkey. Ankara says it is within its sovereign rights to explore for resources in areas it considers its continental shelf.

Greek Prime Minister Kyriakos Mitsotakis said earlier on Tuesday that unless Turkey backed down, European Union sanctions against its NATO ally could be inevitable.

"As long as Turkey continues to take this path, sanctions on Turkey will be a one-way street," he told German Foreign Minister Heiko Maas, who was visiting Athens.

Greece and Turkey have had testy relations for decades, with occasional flare-ups. There was a sharp exchange of words earlier this year when thousands of migrants Turkey hosts tried to force their way into Greece.

They disagree over ethnically-partitioned Cyprus as well. Greece is also angry over a Turkish-Libyan deal carving out maritime boundaries that skim the southern Greek island of Crete.

(Reporting by Michele Kambas; Editing by Mark Heinrich)