Greece's sniping at Turkey for converting the ancient cathedral of Aghia Sophia in Constantinople into a mosque has drawn return fire as the battle there escalated while it was cooling down over Turkish provocations in the Aegean and East Mediterranean.

After 86 years as a museum – having been a mosque for 481 years after the city the rest of the world now calls Istanbul fell to Turkish invaders – the venerable Orthodox church and symbol of Christianity in the Byzantine world opened to Muslim prayers.

That began July 24 after President Recep Tayyip Erdogan, in a move his critics was aimed at mollifying his hard-core religious base despite international denunciation, ordered the conversion, backed by the country's high court who deferred to him.

Greece's New Democracy issued hard words over the move but had not forcefully fought it before the change, although now is trying to find some way to respond too late to make it revert to a museum again.

With tension between the countries already rising over Turkish plans to drill for oil and gas off Greek islands, on hold for now, church bells tolled in mourning across Greece as Erdogan joined prayers at the building, the news agency Reuters reported.

“Greece showed once again its enmity towards Islam and Turkey with the excuse of reacting to Aghia Sophia Mosque being opened to prayers,” Turkish Foreign Ministry spokesman Hami Aksoy said in a written statement, not noting the oddity of using the Greek word for saint in the same title as calling the cathedral a mosque.

The Turkish ministry strongly condemned hostile statements by the Greek government and Parliament members to stir up the public, and the burning of a Turkish flag in the Greek city of Thessaloniki, it said.

The Greek Foreign Ministry, firing back, said, “The international community of the 21st Century is stunned to observe the religious and nationalist fanatic ramblings of today’s Turkey,” Erdogan saying he doesn't care what anyone thinks and no move to stop him.

Thes ceremony sealed Erdogan’s ambition to restore Muslim worship at the site, which most Greeks view as central to their Orthodox Christian religion, the news agency said, after Prime Minister Kyriakos Mitsotakis also called Turkey a “troublemaker,” and the conversion of the site an “affront to civilization of the 21st Century.”