Turkish President Tayyip Erdogan declared Istanbul's Hagia Sophia open to Muslim worship on Friday after a court ruled that the building's conversion to a museum by modern Turkey's founding statesman was illegal.
Below are some reactions to the court's ruling and Erdogan's announcement.
"This is a choice which offends all those who also recognise the monument as a World Heritage Site. And of course it does not only affect relations between Turkey and Greece, but its relations with the European Union" - Greek Prime Minister Kyriakos Mitsotakis.
"We are disappointed by the decision by the government of Turkey to change the status of the Hagia Sophia... We understand the Turkish Government remains committed to maintaining access to the Hagia Sophia for all visitors, and look forward to hearing its plans for continued stewardship of the Hagia Sophia to ensure it remains accessible without impediment for all" - State Department Spokesperson Morgan Ortagus.
Russian Orthodox Church
"It is a real shame that the concerns of the Russian Orthodox Church and other Orthodox churches were not heard. This decision, alas, is not aimed at reconciling existing differences, but on the contrary, may lead to even greater divisions" - Russian Orthodox Church official Vladimir Legoida
"The ruling by the Turkish Council of State to overturn one of modern Turkey's landmark decisions and President Erdogan's decision to place the monument under the management of the Religious Affairs Presidency is regrettable" - EU Foreign Policy chief Josep Borrell.
"It is a historical appropriation and desecration of a World Heritage monument of particular value to the world's Christians" - Cypriot President Nicos Anastasiades.
"UNESCO calls on the Turkish authorities to open a dialogue without delay in order to avoid a step back from the universal value of this exceptional heritage whose preservation will be reviewed by the World Heritage Committee in its next session" - UNESCO statement.
Soner Cagaptay, director of Turkish research program at Washington Institute for Near East Policy
"Erdogan has been flooding Turkey's public space, education policy and government with a brand of conservative Islam, and Hagia Sophia is the crowning moment of Erdogan's religious revolution which has been unfolding in Turkey for over a decade.
"Just as Ataturk nearly 100 years ago 'unmosqued' Hagia Sophia to underline commitment to his own secularist revolution, to take religion out of politics, Erdogan is now doing nearly the opposite. He is reconverting the building into a mosque to underline his own religious revolution."