Greece said on Friday it was expelling the Libyan ambassador, angered at an accord between Libya and Turkey signed on Nov. 27 that maps out a sea boundary between the two countries close to the Greek island of Crete.
Mohamed Younis AB Menfi had 72 hours to leave the country, Greek Foreign Minister Nikos Dendias told a news briefing. Dendias called the Turkey-Libyan accord a "blatant violation of international law".
The move did not mean Greece was severing diplomatic relations with Libya, Dendias said.
Greece had asked Libya for details of the deal last week.
"The text of this agreement carries the signature of the Libyan foreign minister. It is the same person who, in September, had assured the Greek side otherwise," Dendias said.
The Libyan embassy in Athens said it had no comment.
The expulsion is the latest twist in a saga of Mediterranean states jostling to claim yet-untapped oil and gas in the region.
Turkey and the internationally recognised government of Libya signed the accord defining their boundaries and a deal on expanded security and military cooperation, a step Turkey said was protecting its rights.
Greece immediately shot back, calling the accord absurd because it ignored the presence of Crete between the coasts of Turkey and Libya.
"The (geographical) coordinates of this attempt to define maritime boundaries reaffirms this deal is a blatant violation of the (U.N.) Law of the Sea and the sovereign rights of Greece, and other countries," Dendias said.
Egypt and Cyprus have also registered their disagreement with the pact.
Greece and Turkey are at odds over a host of issues ranging from mineral rights in the Aegean Sea to ethnically-split Cyprus. Tensions are also running high because of Turkish drilling off Cyprus, and the European Union has prepared sanctions against Turkey in response.
On Thursday, Cyprus said it was petitioning the International Court of Justice to safeguard its offshore rights.