Turkey is expanding its controversial exploration activities in the East Mediterranean despite warnings from the European Union that it risks sanctions unless it halts the search in disputed waters.
The Turkish seismic vessel Oruc Reis, which had been scheduled to end its survey on Thursday, will now remain at sea until 27 October.
The Turkish Navy said in a maritime announcement — called a Navtex — that two other support vessels, the Ataman and Cengiz Han, will also continue work in an area south-east of the Greek island of Rhodes.
The Oruc Reis has become a symbol of Ankara's exploration push in the East Mediterranean where significant gas finds in the past decade have exacerbated long-standing territorial disputes with Greece and the divided island of Cyprus.
Greece says Turkey is breaking international law by prospecting in Greek waters, including near the island of Meis — also known as Kastellorizo.
The Ankara administration has said its explorations activities are within the Turkish continental shelf, arguing the tiny island of Meis should not count for imposing Greek sovereignty in the waters.
The initial deployment of the Oruc Reis in August triggered a weeks-long diplomatic crisis, which was eased after the vessel returned last month.
However, the seismic vessel was dispatched again last week, ending hopes for a quick diplomatic solution.
Greek Prime Minister Kyriakos Mitsotakis asked the EU on Wednesday to look into suspending its customs union with Turkey.
Turkey stepped up exploration activities after Greece and Egypt signed a controversial maritime delimitation deal.
Declaring the Greek-Egyptian deal "null and void," Turkey authorised the Oruc Reis to resume its controversial search.
Ankara had recalled the Oruc Reis in August to “allow for diplomacy” before an EU summit at which Cyprus sought sanctions against Turkey.
The vessel was the dispatched again, prompting an angry rebuke from Greece, France and Germany.
After the summit, the EU said it would impose economic sanctions on Turkey if it continued its operations in the region.