Tension remained high Tuesday between Greece and Turkey, both of whom have warships in the eastern Mediterranean after Turkey sent a research vessel to carry out seismic research for energy resources in an area Greece says is on its continental shelf.

Ankara announced on Monday that its research vessel Oruc Reis and two support vessels would be operating in the Mediterranean Sea between Cyprus and Greece until Aug. 23. The vessel arrived in the area Monday morning, escorted by Turkish warships.

Greece slammed the decision as an illegal act that infringed on its sovereign rights, saying the Turkish research vessel was inside an area covered by the Greek continental shelf. Greek warships were in the area and were monitoring the Oruc Reis, and the military was on alert, officials said.

In this photo taken Monday, July 27, 2020, Turkey's research vessel, Oruc Reis, anchored off the coast of Antalya on the Mediterranean, Turkey. A top Turkish official said Tuesday that Turkey will suspend research for oil and gas exploration in disputed waters in the Eastern Mediterranean. President Recep Tayyip Erdogan told his aides to "be constructive and put this on hold for some time," presidential spokesman Ibrahim Kalin told Turkish broadcaster CNN Turk. (AP PhotoBurhan Ozbilici)

In this photo taken Monday, July 27, 2020, Turkey's research vessel, Oruc Reis, anchored off the coast of Antalya on the Mediterranean, Turkey. A top Turkish official said Tuesday that Turkey will suspend research for oil and gas exploration in disputed waters in the Eastern Mediterranean. President Recep Tayyip Erdogan told his aides to "be constructive and put this on hold for some time," presidential spokesman Ibrahim Kalin told Turkish broadcaster CNN Turk. (AP PhotoBurhan Ozbilici)

NATO allies and neighbors Greece and Turkey have traditionally had testy relations and have been at odds for decades over a wide variety of issues. The two have come to the brink of war three times since the mid-1970s, including once over drilling exploration rights. Recent discoveries of natural gas and drilling plans across the east Mediterranean have led to renewed tension.

Ankara has been angered by a deal Greece signed with Egypt last Thursday delineating their bilateral maritime boundaries and exclusive economic zones for rights to the exploitation of resources. Last year, Turkey signed a similar deal with the U.N.-backed Libyan government in Tripoli, sparking outrage in Greece, Egypt and Cyprus, which said the agreement infringed on their economic rights in the Mediterranean. The European Union had said the deal was a violation of international law that threatened regional stability.

At the heart of the issue is how a country’s continental shelf is calculated and whether islands should be included in the calculation. Turkey argues they should not, a position that Greece says violates international law.

Greek Prime Minister Kyriakos Mitsotakis spoke with Greek President Katerina Sakellaropoulou Tuesday to inform her of the situation in the eastern Mediterranean, his office said. He was also to speak with the heads of the country’s political parties.

Turkish President Recep Tayyip Erdogan, speaking after a four-hour Cabinet meeting Monday night, warned that Turkey would not confine its offshore exploration efforts to its immediate coastline, but otherwise appeared conciliatory.

“Let’s come together as Mediterranean countries. Let’s find a formula that’s acceptable for everyone, that protects everyone’s rights,” he said in a televised speech.

He added: “We are always there and ready for the solution of disputes through dialogue and on a fair basis. We will continue to implement our own plans in the (eastern Mediterranean) and in the field of diplomacy until common sense prevails in this regard.”