Türkiye announced the start of restoration work on Hagia Sophia, one of the most important historical sites in its largest city, Istanbul, local media reported on Monday.

The restoration project, initiated by the Turkish Culture and Tourism Ministry, aims to "eliminate the centuries-old fatigue" of the 1,500-year-old Hagia Sophia, the Hurriyet Daily News reported.

According to officials, the restoration and maintenance work, which could span over 50 years, will be carried out gradually, section by section, without a complete closure of the site.

The monument, which initially served as a cathedral and later as an Ottoman imperial mosque, reopened as a museum in 1935, unveiling some unique features of Ottoman and Byzantine art.

It was turned into a mosque again in 2020.

Critics have long accused the ruling Islamic-rooted Justice and Development Party (AKP) of President Recep Tayyip Erdogan of harbouring a hidden agenda to turn the Hagia Sophia back into a mosque as a symbol of Turkey's status as a majority Muslim nation, AFP reported.

Hagia Sophia, located on the European side of Istanbul, is one of the most visited tourist sites in the city.