Greece has told UN Secretary-General Antonio Guterres that Turkey is directly challenging its sovereignty over islands in the Aegean Sea. A four-page letter signed by Greece’s UN representative Maria Theofili accused Turkey of pursuing a hostile and “revisionist” policy that is destabilising the region, AP reported. “Greece solemnly calls upon Turkey to stop questioning Greece’s sovereignty over its the Aegean Islands, in particular through legally baseless and historically false assertions to abstain from threatening Greece with war,” the letter said. “Highly threatening acts by Turkey repeated overflights of Greek territory by fighter jets in contravention to international law.” Turkey's National Security Council, or MGK, said current and future military operations on its southern borders are not aimed at its neighbours' sovereignty but are necessary for Turkish security. Greece and Turkey have been at odds for decades over sea boundaries. However, the disagreement escalated in 2020 as oil and gas exploration in the eastern Mediterranean intensified. Turkey is demanding that Greece demilitarise its eastern islands, maintaining the action is required under 20th-century treaties that ceded sovereignty of the islands to Greece. The Greek government calls the demand a deliberate misinterpretation and has accused Turkey, a fellow Nato member, of stepping up hostile actions in the area. Dispute over drilling rights The Greek-Turkish dispute largely centres around oil and gas drilling rights in the eastern Mediterranean, specifically around Greek islands near Turkey’s coastline. A Turkish survey mission two years ago triggered a tense naval stand-off that western allies had warned ran the risk of turning into a military conflict. In response to the energy crisis worsened by the war in Ukraine, Greece has pledged to temporarily reverse a move to phase out coal and step up hydrocarbon exploration along its western coastline. Turkey's MGK statement followed President Recep Tayyip Erdogan's statement on Monday that Ankara would soon launch new military operations on its southern borders to expand 30km deep safe zones and combat what he described as terrorist threats there. Turkey President Recep Tayyip Erdogan said Ankara would soon launch new military operations on its southern borders to combat what he described as terrorist threats. Any operations are expected to focus on northern Syria, where Turkey has launched several incursions since 2016, mainly aimed at the US-backed Kurdish People's Defence Units, or YPG. Ankara views the YPG as similar to the Kurdistan Workers’ Party, or PKK, a group that has been waging an insurgency in southeast Turkey since 1984. It designates both groups as terrorist organisations. The YPG is a key element of the Kurdish-led coalition, which the US largely relied on to fight ISIS.