Greece accused Turkey of infiltrating its airspace late Thursday after four jets flew over disputed islands in the northeastern part of the Aegean Sea, according to the Greek Ministry of Defense, which also said that two of the aircraft were armed. The alleged flyover of the islands adds to the centuries-old feud between the two neighboring NATO nations in the Middle East.

“Ankara’s provocative actions are meant to tell the world that Turkey does not recognize the existing air and sea borders in the Eastern Mediterranean,” said Greece’s former deputy military chief of staff Frangoulis Frangos, according to a report Friday by Russian news outlet Sputnik. 

The infiltration is the first of 2016 and adds to the more than 1,300 airspace violations that happened last year over a 10-mile airspace zone around the Greek islands in the Aegean Sea that Turkey refuses to recognize. More than 30 of those were directly inside the country's sovereign and non-disputed territory. In all, airspace violations from 2014 had doubled to more than 2,400 in 2015, according to the Sputnik report.

In November a Russian jet was shot down by a Turkish air force F-16 after it allegedly strayed into Turkey from Syria, adding to diplomatic strain between NATO and Russia over conflict in Syria and Ukraine.

At the time, Russian President Vladimir Putin, who has had generally tepid relations with Turkey, said the incident would have “serious consequences for Russian-Turkish relations.” The downing of the plane followed numerous incidents of Russian aircraft flying into Turkish territory, which came with stern warnings from Ankara.

Adding to the problems between the three countries is Russia's attempts to cozy up to Athens in order to complete a deal to build a gas pipeline from southern Russia into eastern Greece. The deal, which is still on the table, caused major issues within the EU and NATO as it demonstrated how Moscow was using economic rewards of cheap oil in order to pull Athens out of the European sphere of influence.