President Tayyip Erdogan said on Saturday Turkey will not back down to threats of sanctions nor to incursions on its claimed territory in the Mediterranean Sea, where it is in a standoff with EU-member Greece over oil and gas exploration rights.
European Union foreign ministers on Friday said Ankara's actions were antagonistic and dangerous after a meeting requested by Athens.
Tensions between NATO members Greece and Turkey have risen in the past week after Turkey sent the Oruc Reis survey vessel, escorted by warships, to map out possible oil and gas drilling in territory over which both countries claim jurisdiction.
"We will never bow to banditry on our continental shelf. We will not back down against the language of sanctions and threats," Erdogan said in the northeastern city of Rize.
The Oruc Reis, which is between Cyprus and the Greek island of Crete, will continue work until Aug. 23, he added. The vessel has been shadowed by Greek frigates and on Wednesday warships from the two sides were involved in a mild collision.
EU foreign ministers met via video conference on Friday and said Turkey's naval movements would lead to a "heightened risk of dangerous incidents".
They said a deterioration in the relationship with Turkey was having far-reaching strategic consequences for the entire European Union, well beyond the eastern Mediterranean.
Relations between Greece and Turkey have long been fraught with tension. Disputes have ranged from boundaries of offshore continental shelves and airspace to the ethnically split island of Cyprus. In 1996 they almost went to war over ownership of uninhabited islets in the Aegean Sea.