ISTANBUL — In a controversial verdict, a Turkish court has annulled the museum status of Hagia Sophia in Istanbul, a world-famous cultural site, paving the way for its conversion into a mosque.

According to state-run Anadolu Agency, Turkey's top administrative court annulled a 1934 presidential decree converting Hagia Sophia into a museum.

Shortly after the ruling, Turkey's President Recep Tayyip Erdogan issued a presidential decree transferring the management of the site from the Ministry of Culture to the Presidency of Religious Affairs, paving the way for its conversion. Erdogan has long been a proponent of the move.

The judgment is being seen to have been influenced by the aggressive campaign by Turkey’s Islamists led by President Recep Tayyip Erdogan, calling for the change.

The Hagia Sophia was the Roman Empire's first Christian cathedral and is among the best known Byzantine structures in the world. It switched from a Greek Orthodox cathedral to a mosque in 1453. The historic site then became a museum in 1935.

Hours before the announcement, UNESCO called on Turkey to avoid changing the "outstanding universal value" of the site and requested "prior notification," signaling that it could change the Hagia Sophia's status on the World Heritage List.

The UNESCO also warned that it must be notified of any change in the status of Istanbul’s sixth-century Hagia Sophia museum and the changes may have to be reviewed by its World Heritage committee, the United Nation’s cultural body told Reuters late on Thursday.

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.

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.

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

In a statement released Wednesday, US Secretary of State Mike Pompeo urged Turkey to maintain the UNESCO World Heritage Site "as an exemplar of its commitment to respect the faith traditions and diverse history that contributed to the Republic of Turkey, and to ensure it remains accessible to all."

He said the site's museum status had enabled people from all over the world to see a "magnificent achievement."

"This extraordinary site is a testament to religious expression and to artistic and technical genius, reflected in its rich and complex 1,500-year history," he said.

"The United States views a change in the status of the Hagia Sophia as diminishing the legacy of this remarkable building and its unsurpassed ability — so rare in the modern world — to serve humanity as a much-needed bridge between those of differing faith traditions and cultures." — Agencies