Greece has accused neighbour Turkey of undermining efforts to ease a crisis over drilling rights in the eastern Mediterranean after the announcement that a Turkish survey vessel is being prepared to renew a research mission in disputed waters.
The Turkish research ship Oruc Reis will operate "from 12 to 20 October" in the same region it was exploring in August and September, including the area south of the Greek island of Kastellorizo, according to the message sent by the maritime alert system NAVTEX.
Greece’s Foreign Ministry on Monday called the decision a "major escalation and a direct threat to peace and security in the region".
Tensions flared between Athens and Ankara from August 10 to mid-September following the deployment by Turkey of the seismic research vessel, which was escorted by warships, to carry out explorations off this Greek island, 2 km from the Turkish coast, an area potentially rich in natural gas.
Greece claims sovereignty over the waters around Kastellorizo, but Turkey rejects this, insisting that it has more extensive rights in the eastern Mediterranean because of its longer coastline.
Ankara began by deploying the Oruc Reis and military ships to the disputed waters on August 10 and extended their mission, ignoring repeated calls from the European Union and Athens to desist.
The ship will be joined on the next "seismic sounding" mission by two other ships named Ataman and Cengiz Han, according to NAVTEX.
The Oruc Reis had returned to the Turkish coast last month, while in waters claimed by Greece, in what many hoped would be a sign of de-escalation to resolve the crisis.
Turkish President Recep Tayyip Erdoğan said the withdrawal was intended to give diplomacy a chance.
Turkish leaders also explained that the ship would simply carry out planned maintenance, and that it would return to the eastern Mediterranean to continue its work.
But there was hope that tensions could be diffused when Ankara and Athens agreed to hold negotiations last month, partly as a result of German-led diplomatic efforts to defuse the crisis.
The talks had been delayed since 2016 and were supposed to resume in Istanbul but no date had ever been given.
The highest level of exchanges since the row began took place last week when Turkish and Greek foreign ministers met on the margins of a security forum in Bratislava, Slovakia.
At a summit earlier this month, the EU threatened Ankara with sanctions if Turkey fails to halt energy exploration in waters claimed by Cyprus and Greece.
Turkey had described the threat as "non-constructive," but its latest decision will add tension to relations between Ankara and Brussels.
Relations are already strained after Erdogan gave his backing last week to the reopening of a resort town in Northern Cyprus left abandoned since the Turkish invasion of the island in 1974.
Cyprus asked the UN to step in to review Turkey's decision to reopen Varosha whose Greek-Cypriot community fled 46 years ago leaving it a ghost town.
In a statement on Tuesday, Josep Borrell, the EU's High Representative for Foreign Affairs, said the EU expressed "grave concern" over the decision, underlining "the importance of the status of Varosha" as set out in UN resolutions.
"The EU supports the speedy resumption of negotiations, under the auspices of the UN, and remains fully committed to a comprehensive settlement of the Cyprus problem within the UN framework and in accordance with the relevant UNSC resolutions, including UNSC resolutions 550 and 789, and in line with the principles on which the EU is founded," it said.
"It expects the same of Turkey."
German Foreign Minister Heiko Maas is due to visit Ankara on Wednesday, according to Turkish state media TRT, for a meeting during which the Eastern Mediterranean issue will take centre stage.