More than 2,500 Muslims prayed at Hagia Sophia in Istanbul early Saturday morning.
According to reports, the worshippers gathered at the monument – a UNESCO world heritage site and now officially a museum – at 4 a.m.
Greece has protested over Quran readings in the past inside what used to be Christendom’s greatest cathedral, built in the 6th century under order of the Byzantine Emperor Justinian.
It served as the seat of the Greek Orthodox Church before it was converted into a mosque after the Ottoman conquest of the Byzantine capital of Constantinople (modern-day Istanbul) in 1453.
It was turned into a museum by the Turkish government in 1935.