Turkish President Recep Tayyip Erdogan visited Hagia Sofia on Sunday just days before the first Muslim prayers are due to be held at the there.
The President paid a visit for inspection, Erdogan took stock of the conversion work, providing pictures showing scaffolding inside the building.
It was unclear whether Erdogan planned to be among some 500 worshippers set to attend Friday prayers.
Turkey’s top court paved the way for the conversion in a decision to revoke the edifice’s museum status conferred nearly a century ago.
The sixth-century building had been open to all visitors, regardless of their faith, since its inauguration as a museum in 1935.
Earlier, Diyanet said the building would continue to be open to all visitors outside the hours given over to prayer.
The UNESCO World Heritage site was built as a cathedral during the Byzantine empire but converted into a mosque after the Ottoman conquest of Constantinople in 1453.