Turkey has claimed half of the Aegean Sea falls under its area of marine influence, escalating a territorial spat with Greece over where to put ocean conservation zones.

The move comes after Greece said it would create marine parks in waters Turkey considers its own.

On Monday, Turkey submitted to UNESCO a so-called maritime spatial plan, an official document which sets the marine areas where activities including fishing, tourism and renewable energy projects can take place. It also underpins the creation of marine protection zones.

Even though the spatial plan does not define the country’s exclusive economic zone, the map prepared by Ankara University reflects several of Turkey’s long-standing territorial claims, many of which conflict with those of neighboring Greece.

Greek officials complained the map effectively splits the Aegean Sea in half, claiming the maritime zones of numerous Greek islands into Turkey’s proposed maritime jurisdiction.

“Ankara’s map is not based on any provision of international law and produces no legal effect,” Deputy Foreign Minister Tasos Chatzivasileiou told Greek radio on Tuesday. “It reflects the long-standing Turkish positions but has no legal force. Greece will move [to respond] at all levels.”

The move comes a week after the Greek Prime Minister Kyriakos Mitsotakis announced that legal procedures for the creation of Greece’s first two marine parks, a contentious issue with neighboring Turkey, will begin this month.

Speaking at the United Nations ocean summit in Nice, Mitsotakis said the two marine parks will be established in the Ionian Sea and in the Southern Cyclades region of the Aegean Sea as a first step.

Greece faced a fierce reaction from Turkey last year when it initially announced plans to set aside some of the waters between the two countries for ecological sustainability. Ankara is contesting the sovereignty of some of the maritime territory involved.

The exact location of the maps has not been made available yet, but, according to Greek officials, the Southern Cyclades park will not involve contested areas. Turkish concerns are more likely to focus on the Dodecanese islands and nearby islets, which were part of earlier proposals but are left out of the Greek government’s current planning.

Turkey asserts that the Greek islands are not entitled to full maritime zones beyond 6 nautical miles. Greece upholds the position that this is against international maritime law.

In the Eastern Mediterranean, Turkey’s map extends to the boundaries outlined in a Turkish-Libyan maritime memorandum signed in 2020, an agreement that Athens rejects as illegal and invalid. It also highlights some areas licensed to the Turkish Petroleum Corporation for exploration activities.

In April, Greece completed its national Maritime Spatial Plan and published the official map, outlining its maritime zones in the Aegean and the Eastern Mediterranean, after years of delays that drew rebuke from the European Commission.

Ankara rejected the Greek plan, arguing that it infringes on Turkey’s claimed maritime jurisdiction in both regions, and criticized what it described as Greece’s unilateral approach.