Turkish leaders on Friday marked the sixth anniversary of the reopening of Istanbul's Hagia Sophia as a mosque with commemorative messages, while authorities announced a new phase in the landmark's ongoing restoration.

President Recep Tayyip Erdoğan said Hagia Sophia had regained its "original identity" six years ago after an 86-year hiatus.

"Hagia Sophia regained its original identity six years ago today after 86 years of longing," Erdoğan said in a social media post. "God willing, this blessed place of worship will continue to fill our skies with the call to prayer forever. May the revival of Hagia Sophia be blessed."

Parliament Speaker Numan Kurtulmuş described the reopening as "not only the restoration of a place of worship but also a powerful expression of embracing our history and civilization."

In a separate social media post, Kurtulmuş called Hagia Sophia Grand Mosque "one of the strongest symbols of a nation's will engraved in history and its loyalty to a centuries-old trust."