ANKARA — Turkish President Recep Tayyip Erdogan on Thursday warned Greece to demilitarize islands in the Aegean Sea, saying he was “not joking” with the admonition.

Turkey says Greece has been building a military presence in violation of treaties that guarantee the unarmed status of the Aegean islands. It argues the islands were ceded to Greece on the condition they remained demilitarized.

“We invite Greece to stop arming the islands that have non-military status and to act in accordance with international agreements,“ Erdogan said on the final day of military exercises taking place near Izmir, on Turkey’s Aegean coast. “I’m not joking, I’m speaking seriously. This nation is determined.”

Greece and Turkey are NATO allies, but the neighboring countries have a history of disputes over a range of issues, including mineral exploration in the eastern Mediterranean and rival claims in the Aegean Sea.

“We warn Greece to stay away from dreams and actions that it will regret, and to come to its senses,” the Turkish leader continued. “Turkey won’t give up on its rights in the Aegean, in the same way that it will not stand back from using its rights stemming from international agreement.”

Greece maintains Turkey has deliberately misinterpreted the treaties and says it has legal grounds to defend itself following hostile actions by Ankara, including a long-standing threat of war if Greece extended its territorial waters.

In Athens, Greek government spokesman Giannis Oikonomou said Greece was dealing with Turkish “provocations” with “calm and determination.”

“It is clear to everyone that our country has upgraded its geostrategic and geopolitical footprint as well as its deterrent capacity to be able at any time to defend its national sovereignty and sovereign rights,” he said.

Meanwhile, Erdogan also reiterated Turkey’s determination to launch a new cross-border offensive in Syria with the goal of pushing back Syrian Kurdish militia and creating a 30-kilometer (19-mile) buffer zone. Turkey regards the militia as an extension of the outlawed Kurdistan Workers’ Party, or PKK.

“We will never allow the establishment of terror corridors along our country’s borders, and we will definitely complete the missing parts of our security zone,” the Turkish leader said.

Erdogan continued: “We hope that none of our real allies and friends will oppose our legitimate security concerns.”

Erdogan has said that Turkey’s new offensive in Syria would target the towns of Tall Rifat and Manbij, which lie west of the Euphrates River and from where the Syrian Kurdish fighters launch attacks on Turkish targets.

Read more: More US Military Bases for Greece Further Riles Testy Erdogan

Greece Releases 16 Maps Illustrating Progressive Turkish Revision

The Greek foreign ministry on Thursday published a series of 16 maps on its website that seek to demonstrate and explain the illegal and revisionist nature of Turkey’s actions and claims concerning the Greek islands and the Aegean from 1973 until the present.

“In an effort to increase the wider public’s awareness of Turkish revisionism, the attached maps depict in a vivid and irrefutable way the Turkish illegal unilateral actions and claims,” a foreign ministry announcement said.

As the announcement explained, the maps begin chronologically with the status quo enshrined in the Lausanne (1923) and Paris (1947) Treaties.

“Turkish claims are then presented, beginning with the illegal licensing of the Turkish state oil company (TPAO) for exploration of oil fields in areas of the Greek continental shelf in the North Aegean in 1973, and continuing with the attempt to usurp Greece’s responsibility for Search and Rescue services in half of the Aegean in the 1980s, the “grey zone” theory in the 1990s, further escalation with the granting of new licenses in the Eastern Mediterranean, the endorsement of the “Blue Homeland” as an official doctrine, the “Turkish-Libyan Memorandum”, reaching as far as the Turkish theory of the demilitarization status of the Aegean islands.

The above-mentioned maps document the extent of Turkish revisionism in order to upend the status quo, violating International Law and the International Law of the Sea, and threatening peace, security and stability in our region,” the ministry said.

The maps can be viewed on the ministry’s website at the following link.