0206 GMT September 19, 2020
Relations between NATO allies Ankara and Athens have been uneasy in recent months but tensions increased over Hagia Sophia and energy riches in the Eastern Mediterranean.
Turkish President Recep Tayyip Erdogan joined thousands for the first Islamic prayers on Friday since Hagia Sophia was reconverted from a museum into a mosque this month, AFP wrote.
Greek Prime Minister Kyriakos Mitsotakis on Friday said what was happening in Istanbul was "not a show of force, but proof of weakness".
Mitsotakis called Turkey a "troublemaker", and the conversion of the site an "affront to civilization of the 21st century", Reuters reported.
The reaction to Hagia Sophia opening for Muslim worship "once again revealed Greece's hostility toward Islam and Turkey," Turkish Foreign Ministry spokesman Hami Aksoy said.
Aksoy "strongly condemned" the burning of the Turkish flag in Thessaloniki and accused Greece of "provoking the public with hostile statements".
"The spoiled children of Europe, who cannot accept renewed prostration in Hagia Sophia, are once again delusional," Aksoy added in a statement.
The Greek Foreign Ministry responded with its own statement, saying the international community is stunned to see Turkey’s “religious and nationalist ramblings”.
The UNESCO World Heritage site was originally the Byzantine Empire's main cathedral before its conversion into a mosque after the Ottoman conquest of Constantinople in 1453.
The founder of modern Turkey ordered Hagia Sophia to be turned into a museum in 1934 but Turkey's highest administrative court on July 10 said the building was registered in property deeds as a mosque, allowing Ankara to change its status once more.
Turkey-Greeceties are also strained over the issue of migration, especially after Ankara reopened its border for refugees to leave for Europe earlier this year.