Turkish Armenian lawmaker Garo Paylan has said that the conversion of Hagia Sophia into a mosque in Istanbul will make life more difficult for Christians in Turkey and for Muslims in Europe.

"A sad day for Christians & for all who believe in a pluralist Turkey," Paylan said on social media after Turkey's President Recep Tayyip Erdogan announced the decision after a court annulled the site's museum status.

"Hagia Sophia was a symbol of our rich history. Its dome was big enough for all."

Built 1,500 years ago as an Orthodox Christian cathedral, Hagia Sophia was converted into a mosque after the Ottoman conquest in 1453.

In 1934 it became a museum and is now a Unesco World Heritage site. Now, once again, it will be a mosque.