ANKARA, Turkey (AP) — Turkish President Recep Tayyip Erdogan formally opened a former Byzantine church in Istanbul as a mosque on Monday, four years after his government had designated it a Muslim house of prayer, despite criticism from neighboring Greece.

Turkey formally converted The Church of St. Saviour in Chora, known as Kariye in Turkish, into a mosque in 2020, soon after it similarly turned Istanbul’s landmark Haghia Sophia into a Muslim house of prayer.

Both conversions drew praise from Muslim faithful but criticism from Greece and other countries who had urged Turkey to protect the important Byzantine-era monuments. Both are listed as U.N. World Heritage Sites.

Like Haghia Sophia, which was a church for centuries and then a mosque for centuries more, the Chora had operated as a museum for decades before it was ordered turned into a mosque. The Chora’s formal launch as a mosque, however, was delayed as the structure then underwent restoration.