Transformation of the Istanbul Hagia Sophia historic monument from a museum to a mosque would be “unacceptable”, a senior official in the Russian Orthodox Church said on July 4.

President Tayyip Erdogan has proposed restoring the mosque status of the UNESCO World Heritage Site, a sixth century building, the Christian Byzantine emblematic consturciton, which became one of most visited world monuments.

“We can’t go back to the Middle Ages now,” Metropolitan Hilarion, chairman of the Moscow Patriarchate’s department for external church relations, said on state television, reported the Interfax news agency.

“We live in a multipolar world, we live in a multi-confessional world and we need to respect the feelings of believers.”

Hilarion said the Russian Orthodox Church did not understand the reason for Hagia Sophia’s transformation and that they believed domestic politics was behind the move.

“We believe that in the current conditions this act is an unacceptable violation of religious freedom,” the cleric concluded.

A Turkish court earlier this week heard a case aimed at transfering the building back into a mosque and will announce its verdict mid-July.

The court case, brought by an NGO, disputes the legality of a decision in 1934, in the early days of the modern secular Turkish state under Mustafa Kemal Ataturk, to convert Hagia Sophia – known in Turkish as Ayasofya – from a mosque into a museum.

However the revolutionary proposal of NGO, backed by President Erdogan, has been criticised by other religious and political leaders.

Ecumenical Patriarch Bartholomew, the spiritual head of some 300 million Orthodox Christians worldwide and based in Istanbul, said converting it into a mosque would disappoint Christians and would “fracture” East and West.

Erdogan has assessed the foreign criticism over the proposal as an attack on Turkey’s sovereignty.

Russian meida reported that the first symbolic Muslim service could take place mid-July.