Greek Prime Minister Kyriakos Mitsotakis criticized Turkey for turning the Byzantine Chora church—which had been a museum for many decades—in Istanbul into a mosque, Kathimerini reported.

The actual decision to turn this medieval church into a mosque was made several years ago, but its final opening as a mosque to the Muslim faithful took place on Monday.

Chora was already a mosque during the Ottoman Empire. But after the secular reforms in the mid 20th century, it was turned into a museum, and its old frescoes and mosaics, which were covered with plaster during the Ottoman times, were reopened.

Greek PM Mitsotakis said that he considers Turkey's move "unnecessary" and “an action which insults Istanbul’s rich history as a crossroads of civilizations."

He said that he will discuss this matter with Turkish President Recep Tayyip Erdogan during his visit to Ankara next week.

"Turning the Chora monastery into a mosque is a bad signal; after all, it is an object of cultural heritage. If we want to have good relations, we must respect the shared values," said the President of Greece, Katerina Sakellaropoulou.

After Erdogan formally opened this church as a mosque on Monday, the Greek foreign ministry said it "alters and insults its character as a UNESCO world cultural heritage monument belonging to humanity."