Historic rivals while also being fellow members of NATO, Turkey and Greece have been at odds over issues ranging from overflights and the status of Aegean islands to maritime boundaries and hydrocarbon resources in the Mediterranean, as well as ethnically split Cyprus.

Ankara has recently accused Athens of arming the demilitarised Aegean islands - something Athens rejects, but Erdogan had not previously accused Greece of occupying them.

"Your occupying the islands does not bind us. When the time, the hour, comes, we will do what is necessary," Erdogan said, speaking in the northern province of Samsun.

Greece reacted by saying it will not follow Turkey in its "outrageous daily slide" of statements and threats.

"We will inform our allies and partners on the content of the provocative statements ... to make it clear who is setting dynamite to the cohesion of our alliance during a dangerous period," the foreign ministry said.

Turkey has recently been angered by what it said is harassment of its jets by Greek forces. Ankara has said that S-300 air defence systems used by Greece had locked on to Turkish jets during a routine flight.

Turkey celebrated Victory Day on Aug. 30, a national holiday commemorating Turkish forces driving out Greek forces in 1922. On Saturday, Erdogan also called on Greece to "not forget Izmir", referring to the Turkish victory.

As Erdogan prepares for what is shaping up to be the biggest electoral challenge of his nearly 20-year rule in 2023, the president has played up achievements in the global stage. He has also stepped up his rhetoric on foreign policy.

Ankara says the Aegean islands were given to Greece under the 1923 and 1947 treaties on condition that it does not arm them. Foreign Minister Mevlut Cavusoglu has repeatedly said Turkey would start questioning Greek sovereignty over the islands if Athens persisted in arming them.

Greek Prime Minister Kyriakos Mitsotakis has said Turkey's position of questioning Greece's sovereignty over the islands is "absurd".