President Tayyip Erdogan declared Istanbul’s Hagia Sophia a mosque on Friday with the first Muslim prayers to begin in two weeks, after a top court ruled the ancient building’s conversion to a museum by modern Turkey’s founding statesman was illegal.

Erdogan spoke on Friday just hours after the court ruling was published, brushing aside international warnings not to change the status of the nearly 1,500-year-old monument that is revered by Christians and Muslims alike.