Pope Francis and Russian Church lament Turkey's Hagia Sophia decision

(Updates with Pope Francis' statement)

Pope Francis said on Sunday that he was "very distressed" over Turkey's decision to convert the Byzantine-era monument Hagia Sophia back into a mosque. 

"My thoughts go to Istanbul. I'm thinking about Hagia Sophia. I am very saddened," the pope said.

Meanwhile, a senior official in the Russian Orthodox Church said Hagia Sophia's losing its museum status is "a blow to global Orthodox Christianity", Bianet reported.

"This is a blow to global Orthodox Christianity because Hagia Sophia to all Orthodox Christians the world over is the same symbol as St. Peter's Cathedral in Rome is to Catholics," Bianet cited Metropolitan Hilarion, chairman of the Moscow Patriarchate’s department for external church relations, as saying.

For the Russian Orthodox Church, this cathedral "remains a temple dedicated to the Christ the Saviour," he said. 

Turkish President Recep Tayyip Erdoğan handed administrative control of the Hagia Sophia to the Diyanet, Turkey's religious affairs directorate on Friday, after the country’s highest administrative court annulled a 1934 cabinet decision under modern Turkey's founder Mustafa Kemal Atatürk to turn the church-turned-mosque into a museum.

Erdoğan has repeatedly called for the UNESCO World Heritage site to be reverted into a mosque and he recited a verse from the Quran at Hagia Sophia in 2018.

"This is an event that may have serious consequences for the entire human civilisation. It is regrettable that the Turkish leader didn't have the statesmanship," the deputy head of the Moscow Patriarchate’s Department for External Church Relations, Archpriest Nikolay Balashov, told Russian news agency Interfax on Friday.

Meanwhile, the World Council of Churches, which represents 350 Christian churches, has called on Erdoğan to reverse his decision and said the move would sow division in a letter to the Turkish president on July 11.

"By deciding to convert the Hagia Sophia back to a mosque you have reversed that positive sign of Turkey’s openness and changed it to a sign of exclusion and division," the World Council of Churches Interim Secretary General Ioan Sauca said.

"The decision to convert such an emblematic place as Hagia Sophia from a museum back to a mosque will inevitably create uncertainties, suspicions and mistrust, undermining all our efforts to bring people of different faiths together at the table of dialogue and cooperation," he said.

There had been increasing requests for Turkey’s government to fulfil a long-standing demand by Turkey’s Islamists, especially in the wake of reports that the gunman who killed Muslim worshippers in New Zealand left a manifesto saying the Hagia Sophia should be free of minarets.

Defending the decision against international criticism, Erdoğan stressed on Friday that the country had exercised its sovereign right in converting the site back to a mosque.

He told a press conference the first Muslim prayers in Hagia Sophia as a newly-reconverted mosque would be held on July 24.

"Like all our mosques, the doors of Hagia Sophia will be wide open to locals and foreigners, Muslims and non-Muslims," he added.