Greek Prime Minister Kyriakos Mitsotakis on Wednesday urged Turkey to show "sense" in a naval showdown in the Eastern Mediterranean over energy exploration which he warned could lead to a military accident.
Tensions were stoked Monday when Ankara dispatched the research ship Oruc Reis accompanied by Turkish naval vessels off the Greek island of Kastellorizo in the eastern Mediterranean.
Greece also deployed warships to monitor the vessel, which is currently sailing west of Cyprus.
"We are vigilantly looking forward to sense prevailing, at last, in our neighbouring country, so that dialogue may be re-initiated in good faith," Mitsotakis said in a statement.
"The risk of an accident lurks when so many military assets are gathered in such a contained area."
The Greek PM said Athens would not seek to escalate the situation, but added: "No provocation will though go unanswered."
Athens has demanded the immediate withdrawal of the Oruc Reis from what it regards as its continental shelf, and has asked for an emergency meeting of EU foreign ministers on the issue.
Greece 'will not suffer blackmail'
"Our country never threatens but will not suffer blackmail either," Mitsotakis said. "We are not alone in this effort."
Earlier Wednesday, EU diplomacy chief Josep Borrell said foreign ministers will hold an extraordinary meeting Friday to discuss the eastern Mediterranean, Lebanon and Belarus.
The office of French President Emmanuel Macron said he would strengthen France's military presence in the region with the cooperation of European partners including Greece.
During a phone with Mitsotakis, Macron "expressed his concern about the tensions caused by Turkey's unilateral decisions on oil exploration, which must stop to allow a peaceful dialogue between neighbouring countries and NATO allies," the French presidency said in a statement.
The incident is the latest spat over energy exploration in the gas-rich eastern Mediterranean, a frequent source of disputes between Turkey and neighbours including Greece, Cyprus and Israel.
Greek Foreign Minister Nikos Dendias will fly to Israel on Thursday for talks, his office said.
Dendias is also to address the issue with US Secretary of State Mike Pompeo in Vienna on Friday.
'No compromise' from Turkey
A similar crisis last month was averted after Turkey pulled the Oruc Reis back to hold talks with Greece and rotating EU chair Germany.
But the mood soured last week after Greece and Egypt signed an agreement to set up an exclusive economic zone in the region.
Turkish Foreign Minister Mevlut Cavusoglu has said his country would step up energy exploration in the eastern Mediterranean and would not "compromise" on its rights.
Turkey has announced the Oruc Reis would carry out activities between August 10 and 23, in an area it considers its own continental shelf.
Mitsotakis on Monday conferred with his military chiefs and spoke with EU Council President Charles Michel and NATO Secretary General Jens Stoltenberg.
Turkish President Recep Tayyip Erdogan sounded a slightly more conciliatory note after a meeting with his own ministers later Monday.
"Let us all come together as Mediterranean countries and find a formula that protects all of our rights," Erdogan said in a national address.
But Erdogan added: "We cannot allow (nations) to ignore a big country like Turkey and try to imprison us to our shores."
The Turkish foreign ministry has said the Greece-Egypt agreement was "null and void".
Egypt, Cyprus and Greece have likewise denounced a contentious deal, including a security agreement, signed last year between Ankara and the UN-recognised government in Libya.
Greece, Cyprus and Israel in January signed an agreement for a huge pipeline project to transport gas from the eastern Mediterranean to Europe despite Turkey's hostility to the deal.