Turkey said on Sunday that its Oruc Reis exploration vessel will now carry out seismic surveys in a disputed part of the eastern Mediterranean until August 27, in a move likely to stoke tensions in the region.
Turkey and Greece, NATO allies, vehemently disagree over claims to hydrocarbon resources in the area based on conflicting views on the extent of their continental shelves in waters dotted with mostly Greek islands.
Earlier this month, Turkey said the Oruc Reis would conduct seismic exploration until August 23 in waters claimed by Greece, Cyprus and Turkey. Athens has called the survey illegal.
On Sunday, the Turkish navy issued a new advisory saying that the work of the Oruc Reis and two other vessels, the Ataman and Cengiz Han, would continue until August 27.
Seismic surveys are part of preparatory work for potential hydrocarbon exploration. Turkey and Greece are also at odds over issues such as overflights in the Aegean Sea and the ethnically divided island of Cyprus.
Turkey has also been exploring for hydrocarbon resources in the Black Sea. On Friday, President Tayyip Erdogan announced the discovery of a 320 billion cubic meter (11.3 trillion cubic feet) gas field, the largest such find in Turkish history.