Hagia Sophia Photograph:( Agencies )
The Hagia Sophia, which was first a cathedral then a mosque after the conquest of Istanbul, is inscribed as a UNESCO World Heritage site as part of an area designated as 'Historic Areas of Istanbul.'
The UN's cultural agency UNESCO warned Turkey on Friday against converting the Byzantine-era Hagia Sophia museum in Istanbul into a mosque, urging dialogue before any decision is taken.
The Hagia Sophia, which was first a cathedral then a mosque after the conquest of Istanbul, is inscribed as a UNESCO World Heritage site as part of an area designated as "Historic Areas of Istanbul."
Turkey's top administrative court is likely to announce on Friday that the 1934 conversion of the Hagia Sophia to a museum was unlawful, two Turkish officials said, paving the way for its restoration as a mosque.
UNESCO said that the Hagia Sophia was on its list of World Heritage Sites as a museum, and as such had certain commitments and legal obligations.
"Thus, a state must make sure that no modification undermines the outstanding universal value of a site listed on its territory," UNESCO said.
"Any modification must be notified beforehand by the state to UNESCO and be reviewed if need be by the World Heritage Committee," it added.
UNESCO said it had expressed its concerns to Turkish authorities in several letters and conveyed the message to Turkey's ambassador to the institution on Thursday.
"We urge Turkish authorities to start a dialog before any decision is taken that could undermine the universal value of the site," UNESCO said.
Hagia Sophia was first constructed as a cathedral in the Christian Byzantine Empire but was converted into a mosque after the Ottoman conquest of Constantinople in 1453.
Turning it into a museum was a key reform of the post-Ottoman authorities under the modern republic's founder Mustafa Kemal Ataturk.
But calls for it to serve again as a mosque have sparked anger among Christians and tensions between the historic foes and uneasy NATO allies Turkey and Greece.
The World Heritage site was at the centre of both the Christian Byzantine and Muslim Ottoman empires and is today one of Turkey's most visited monuments.
The prospect of a change in the museum's status back to a mosque has raised alarm among US, French, Russian and Greek officials, as well as Christian church leaders.