Egypt's top religious body slams Ottoman 'occupation' of Istanbul
The Dar Al-Iftaa, the country's top Sunni Muslim body, slammed the plans as "propaganda" and the continuation of what it said was the "occupation" of Istanbul.
The Hagia Sophia, also known as the Aya Sofya, was built as a church by the Byzantines in the sixth century.
It was later converted to a mosque following the Ottoman conquest of Istanbul, then known as Constantinople.
In 1934, it was converted to a museum as part of efforts by the new Turkish republic to secularise and move away from the country's Ottoman heritage.
"The issue of converting the Hagia Sophia to a mosque was raised decades ago, but it remained a tool and a propaganda weapon in the hands of various politicians in their campaigns to attract voters, especially the religious ones," the Dar Al-Iftaa said in a statement on Sunday.
The religious body's condemnation of the Ottoman "occupation" has stirred controversy among Muslims, many of whom believe the Ottomans were the legitimate rulers of the last Islamic caliphate.
One of the Muslim world's oldest and most influential bodies, the Dar Al-Iftaa is responsible for issuing fatwas, or religious edicts, on all aspects of worship and life.
The statement is the latest manifestation of the fierce rivalry between Turkey and Egypt since President Abdel Fattah Al-Sisi seized power from the country's first democratically-elected president - and Turkish-ally - Mohammad Morsi in a 2013 coup.
Earlier this year, the religious body targeted Turkey over its popular television industry, alleging influential series such as such as "Resurrection: Ertugrul" and "Valley of the Wolves", are part of efforts led by Erdogan to revive the Ottoman Empire.
Erdogan and his supporters "export to the people and nations the idea that they are the leaders of the caliphate, responsible for supporting Muslims worldwide and being their salvation from oppression and injustice, while also seeking to implement Islamic law", the Dar al-Iftaa said.
While Muslims have sporadically been allowed to perform prayers at the UNESCO heritage site in recent years, the issue of converting the Hagia Sophia into a mosque is highly controversial in Turkey.
The issue highlights the sharp divide between conservative Muslims and secularists in the country.
Previous attempts to hold prayers in the museum have also elicited upset from Greece.
This included last month, when Muslims prayers were performed in order to mark the anniversary of the Ottoman conquest of Istanbul.
Turkey and Greece have often locked horns over issues of territorial issues, including over gas drilling in the Mediterranean and over Cyprus.
In recent months, tensions between the two states have risen over the issue of migrants in the region following Turkey's announcement in February that it would no longer stop migrants from attempting to reach Europe from its territory.
President Erdogan last week ordered a study into the museum's conversion into a mosque, according to a local media report denied by the ruling party.
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