An escalating war of words has broken out between Turkey and Greece over islands in the Aegean Sea, with both sides now exchanging accusations and threats in each other's language. Turkish President Recep Tayyip Erdoğan warned Athens on Thursday to demilitarize the islands that he claims were peacefully ceded to Greece. Ankara has accused Greek authorities of building a military presence in violation of the 1923 Treaty of Lausanne and the 1947 Paris Treaty, which guarantee the islands' unarmed status. Erdoğan stated that he was "not joking" and even posted tweets in both Greek and English in a marked harshening of rhetoric against Turkey's neighbor and historic regional rival. "This nation is determined," the Turkish president said on the final day of military exercises near Izmir. Greece has stated that the islands — located within striking distance of a large Turkish landing fleet — cannot be left undefended and have been garrisoned for decades. While the two countries are NATO allies, they have long engaged in disputes over migration, maritime borders and mineral exploration in the eastern Mediterranean. Greece maintains Turkey has deliberately misinterpreted international treaties and says it has legal grounds to defend itself against hostile actions by Ankara. After Erdoğan decided to tweet in Greek, a government spokesperson in Athens described it as "notable". "Greek is known as the language of reason, freedom and justice," Giannis Oikonomou said. "The tactics Turkey has chosen do not fall under any of these categories." Oikonomou had earlier said that Greece was dealing with Turkish "provocations" with "calm and determination." Former Greek Prime Minister Alexis Tsipras even replied to Erdoğan in Turkish. "Greece will protect its sovereignty against all kinds of threats," he wrote on Twitter. "Let's end the provocation and get back to dialogue on the basis of international law." Last month, Erdoğan said he would stop talking to Greek Prime Minister Kyriakos Mitsotakis, after comments the Greek leader made during a trip to the US. "I think we are still very far from that point, far from the tension we had in the summer of 2020," Mitsotakis said in reference to a time when tensions flared between Greece and Turkey over gas exploration rights in the eastern Mediterranean. "Today, everyone needs to show restraint," he said, commenting on tensions between Athens and Ankara, "especially at a time when we are facing a very big challenge at NATO with the Russian invasion of Ukraine. We must be united." — Euronews