Cypriot Foreign Minister Markos Kyprianou said on Wednesday a dispute over offshore oil exploration was damaging Turkey's efforts to join the European Union and showed Ankara was becoming unpredictable.
Cyprus, an EU member state, is blocking Turkey's EU accession talks on energy issues because of the dispute.
It has accused Turkey of harassing hydrocarbon research vessels four times since Nov. 13. Turkey has said the ships, on two previously known occasions, encroached on its continental shelf.
"The reaction of Turkey is illegal, unjustified and definitely this gunboat diplomacy belongs to the 19th century, not to a modern state of the 21st century which wishes to join the EU," Kyprianou told Reuters in an interview.
Asked if he feared there would be more incidents over the oil exploration, he said: "I don't think we can predict how Turkey will react or behave.
"I am afraid they are becoming very unpredictable, which again is not compliant with their obligations to have good neighbourly relations, which is something which is demanded of them by the EU."
Kyprianou said Cyprus was being harassed and obstructed by Turkey in its oil exploration and would not agree to let accession talks on energy start until the dispute was resolved.
France, which holds the EU's rotating presidency, had hoped to open energy talks with Turkey before the end of this year.
Cyprus's Greek and Turkish Cypriot communities have lived apart since a Turkish invasion in 1974 triggered by a brief Greek-inspired coup. Greek Cypriots represent Cyprus in the EU and have the power to veto the enlargement talks.
Kyprianou said Cyprus was not blocking other areas of talks and would judge matters on a case-by-case basis.
"If Turkey behaves as a country of the 21st century aspiring to be member of the EU, even that (the energy chapter) could be unblocked," he said.
Accession talks between the EU and Turkey have been moving slowly, with Brussels saying Turkey has put reforms demanded by the EU on the back-burner.
Turkish officials accuse the EU of double standards over membership criteria and say anti-Turkish feelings in Europe have dampened Turks' enthusiasm for Europe.
Turkey has said Cyprus' oil exploration could upset reunification efforts because natural resources should belong to all residents of the island — Greek and Turkish Cypriots.
But Kyprianou said the oil exploration was another reason to move on with talks to reunify the island.
"The ultimate aim is, if oil deposits are found and if we manage to explore them in a commercial way, these should benefit eventually the whole of the population of the island because we hope that by that time the Cyprus problem will be solved," he said.
