Turkey has hit back at Greek and EU officials, denying claims it is acting illegally by drilling for gas in waters off Cyprus.

The country’s foreign ministry criticised EU condemnation of its efforts to tap the region for potentially lucrative energy resources, saying the bloc could not be considered an impartial mediator for the divided island.

In a statement that will cause dismay in Brussels, Ankara vowed to press ahead with offshore exploration to safeguard the rights of Turkish Cypriots to the natural resources.

Tensions over hydrocarbons escalated sharply after the discovery of possibly huge gas reserves off Cyprus, where there are conflicting claims over territorial waters.

The Turkish president, Recep Tayyip Erdoğan, has repeatedly warned international oil companies commissioned by the Greek Cypriot government not to participate in the search for underwater deposits.

ExxonMobil, Total and Eni are among the firms that have won licences to search in blocks around the island. Last year Turkish gunboats were dispatched to prevent Eni, an Italian oil company, from conducting drilling operations.

On Wednesday Ankara dug in its heels, pledging a second drilling vessel, the Yavuz, would expand exploration activities. The ship dropped anchor off the island’s north-eastern Karpas peninsula on Monday.

Its arrival came two months after another ship, the Fatih, began drilling off Cyprus’s west coast escorted by a frigate.

Greece’s newly elected prime minister Kyriakos Mitsotakis discussed the growing tensions in the eastern Mediterranean with Theresa May when his British counterpart called to congratulate him on the victory of his centre right New Democracy party in snap polls on Sunday. Government sources said Mitsotakis used the opportunity to highlight the role of the European Union in the wider region.

In Athens, Ankara and Nicosia, diplomats fear the showdown could trigger military confrontation, and worry Erdoğan may be looking to provoke crisis to divert attention from domestic troubles.

Cyprus has waged a far-reaching diplomatic campaign, accusing Turkey of breaching the republic’s sovereignty by encroaching on its exclusive economic zone in its efforts to stake a claim to the resources.

Ankara insists it is acting within its own continental shelf or in territorial waters where Turkish Cypriots would also be entitled to an equal share of any finds. Its determination to press ahead with drilling follows Nicosia’s decision to take legal action, with arrest warrants issued for the crew of Fatih.

The island has been ethnically split between its majority Greek population in the south and Turks in the north since an Athens-inspired coup aimed at union with Greece prompted Ankara to order a full-scale invasion in 1974 and seize the northern third. Only Turkey recognises the breakaway state of northern Cyprus.

Last month the EU threatened economic sanctions against Ankara.

On Tuesday, Washington urged all parties to exercise restraint. “The United States remains deeply concerned by Turkey’s repeated attempts to conduct drilling operations in the waters of Cyprus,” the state department said in a statement. “We urge Turkish authorities to halt these operations and encourage all parties to act with restraint and refrain from actions that increase tensions in the region.”

Brussels also voiced “grave concern” over Turkey’s declared intention “to illegally conduct” a new drilling operation off the island.

In a statement on Monday the EU’s foreign policy chief, Federica Mogherini, pledged the bloc would continue to stand by its most easterly member, describing the dispatch of the second drilling ship as an “unacceptable escalation”.

“We call on Turkish authorities, once again, to refrain from such actions, act in a spirit of good neighbourliness and respect the sovereignty and sovereign right of the Republic of Cyprus in accordance with international law,” she said. “The European Union will respond appropriately and in full solidarity with Cyprus.”

France also stepped in this week, calling on Turkey to avoid any action that would endanger regional stability. Ankara and Paris have been at loggerheads over the issue since the French president, Emmanuel Macron, came out in support of Cyprus at a meeting of heads of EU Mediterranean states last month.

“We want to take the road of calm. We want to resolve this peacefully between Greece, Turkey and Cyprus,” said one EU ambassador based in Athens. “That’s what we want, but frankly, who knows?”