The agreement, originally signed with the UN-recognised Government of National Accord in 2019 but long opposed by Libya's eastern parliament, was ratified on Tuesday after that body reversed its position. Turkey's Foreign Ministry welcomed the decision.
The accord creates a maritime corridor between southern Turkey and northern Libya, an area where estimates suggest natural gas reserves worth several hundred billion US dollars lie beneath the seabed. Turkey and Libya plan to jointly explore and exploit those resources.
The corridor disregards Greek islands including Crete, Karpathos and Rhodes. Greece's government said it firmly rejects the agreement and has the backing of the European Union.
"The European Union has described the Turkish-Libyan memorandum as null and void, stressing that it violates the sovereign rights of third states and is not consistent with the Law of the Sea," the Greek Foreign Ministry posted on X.
EU foreign policy chief Kaja Kallas also weighed in, writing on X: "I raised yesterday's Libyan vote on a maritime MoU with Türkiye and stressed that it infringes upon the sovereign rights of third states."
The dispute centres on competing interpretations of international maritime law. Greece cites the UN Convention on the Law of the Sea (UNCLOS), which grants inhabited islands the same rights to an exclusive economic zone as mainland territory. Turkey, which has never signed UNCLOS, argues that granting full EEZ rights to every small Greek island off its coast would cut Turkey off from the open sea.
The agreement also threatens the planned EastMed pipeline, which would carry natural gas from Israel and Cyprus through Greece to Europe, as the corridor crosses its proposed route.
Turkey's relationship with Libya has deepened since its military intervention in 2019. Turkish construction companies have won billions of dollars in reconstruction contracts, and the Turkish state oil company TPAO is working with Libya's National Oil Corporation on seismic surveys. Turkey has also become a military partner for eastern Libyan commander Khalifa Hifter, pushing back against Egyptian and Russian influence.