Bringing tension to a near-boiling point amid fears of a conflict, Cyprus has issued arrest warrants for the crew of a Turkish drill ship in the island country’s Exclusive Economic Zone (EEZ) where foreign companies are licensed to hunt for oil and gas.

“We can confirm that warrants were issued. It’s a double digit number,” a Cypriot official who wasn’t named told the news agency Reuters, declining further comment after Turkey warned there would be a swift response if there was any attempt to apprehend the crew.

Turkey said on June 10 that reports of the arrest warrants – which had at that point not been confirmed by Nicosia – “crossed the line,” with the United States and European Union backing Cyprus’ right to issue licenses.

One of those is held by the US energy giant ExxonMobil which has already reported a major find there. The Turkish energy research ship is being guarded by a Turkish warship, with President Recep Tayyip Erdogan planning to send another drilling vessel, despite the presence of US Sixth Fleet ships in the region.

“No one should have any doubt that the necessary response will be given, in case of such an insolence,” a Turkish foreign ministry spokesperson said earlier. A Turkish drill ship, the Fatih, has been anchored west of Cyprus since last month, and another drill vessel, the Yavuz, is scheduled to be deployed east of the island soon.

Both areas are claimed by the Greek Cypriot government as its EEZ, parts of which Turkey doesn’t recognize, as it also doesn’t the United Nations Laws of the Sea unless citing them to back its own interests.

Turkey claims an area west of Cyprus is its own continental shelf with anxiety rising that the dispute could draw in Greece, which, along with Turkey and the United Kingdom, the former Colonial ruler which still has a military base on the island, are security guarantors.

Turkish Foreign Minister Mevlut Cavusoglu said that any Cypriot deal for oil and gas exploration in the Eastern Mediterranean that excludes Turkey is “invalid,” ramping up the rhetoric again.

Media reports said Cavusoglu dismissed the arrest warrants and said, “We will not back down and we will take all the necessary steps.” He added: “The Greek Cypriots should know their limits.”

During an inspection of the Hellenic Navy fleet June 14,, Greek President Prokopis Pavlopoulos urged Turkey to abide by international and EU law with no sign that would happen as Erdogan has defied calls to back off.