Turkish President Recep Tayyip Erdogan on Friday formally re-converted Istanbul's sixth-century iconic Hagia Sophia into a mosque, hours after a high court annulled a 1934 decision that had turned it into a museum.

Erdogan signed a decree handing over Hagia Sophia to Turkey's Religious Affairs Presidency and declaring it open to Muslim worship.

THIS IS A BREAKING NEWS UPDATE. AP's earlier story follows below.

Turkey's highest administrative court on Friday issued a ruling that paves the way for the government to convert Istanbul's iconic Hagia Sophia — a former cathedral-turned-mosque that now serves as a museum — back into a Muslim house of worship.

The Council of State threw its weight behind a petition brought by a religious group and annulled a 1934 cabinet decision that turned the 6th-century building into a museum. 

Dozens of people who awaited the court's ruling outside the Hagia Sophia jubilantly chanted "Allah is great!" when the news came out. Orthodox Christians expressed deep dismay.

Turkish President Recep Tayyip Erdogan has demanded that the the hugely symbolic world heritage site should be turned back into a mosque despite widespread international criticism, including from the United States and Orthodox Christian leaders. The move could also deepen tensions with neighboring Greece.

Cypriot Foreign Minister Nikos Christodoulides, a Greek Cypriot, posted on his official Twitter account that Cyprus "strongly condemns Turkey's actions on Hagia Sophia in its effort to distract domestic opinion and calls on Turkey to respect its international obligations." 

Christodoulides said Turkey's "escalating, flagrant violation of its international obligations is manifested in its decision to alter the designation of Hagia Sophia, a world heritage site that is a universal symbol of the Orthodox faith."

Turkish President Recep Tayyip Erdogan was scheduled to deliver an address to the nation later on Friday.

Nationalist and conservative groups have long been yearning to hold prayers at Hagia Sophia, which they regard as part of the Muslim Ottoman legacy. Others believe the UNESCO World Heritage site should remain a museum, as a symbol of Christian and Muslim solidarity.

The group that brought the case to court had contested the legality of the 1934 decision by the modern Turkish republic's secular government ministers and argued that the building was the personal property of Ottoman Sultan Mehmet II, who conquered Istanbul in 1453.

The court ruled that Hagia Sophia was the property of a foundation managing the Sultan's assets and was opened up to the public as a mosque.

The Istanbul-based Ecumenical Patriarch Bartholomew I, considered the spiritual leader of the world's Orthodox Christians, warned in late June that the building's conversion into a mosque "will turn millions of Christians across the world against Islam." 

Patriarch Kirill, the leader of the Russian Orthodox Church, called for "prudence" and the preservation of the "current neutral status" for the Hagia Sophia, which he said was one of Christianity's "devoutly venerated symbols." In a statement this week, he said: "Russia is a country with the majority of the population professing Orthodoxy, and so, what may happen to Hagia Sophia will inflict great pain on the Russian people."

U.S. State Secretary Mike Pompeo said last month that the landmark should remain a museum to serve as bridge between faiths and cultures. His comments sparked a rebuke from Turkey's Foreign Ministry, which said Hagia Sophia was a domestic issue of Turkish national sovereignty.

Erdogan, a devout Muslim, has frequently used the Hagia Sophia issue, which sits at the heart of Turkey's religious-secular divide, to drum up support for his Islamic-rooted party. He has pledged to revert the structure's status to a mosque several times but said his government would await the court's decision before taking steps.

Some Islamic prayers have been held in the museum in recent years and in a major symbolic move, Erdogan recited the opening verse of the Quran in the Hagia Sophia in 2018. 

Built under Byzantine Emperor Justinian, Hagia Sophia was the main seat of the Eastern Orthodox church for centuries, where emperors were crowned amidst ornate marble and mosaic decorations.

Four minarets were added to the terracotta-hued structure with cascading domes and the building was turned into an imperial mosque following the 1453 Ottoman conquest of Constantinople — the city that is now Istanbul. 

The building opened its doors as a museum in 1935, a year after the Council of Ministers' decision. 

Mosaics depicting Jesus, Mary and Christian saints that were plastered over in line with Islamic rules were uncovered through arduous restoration work for the museum. Hagia Sophia was the most popular museum in Turkey last year, drawing more than 3.7 million visitors. 

News reports have said the conversion could occur in time for prayers on July 15, when Turkey marks the quashing of a coup attempt in 2016.

A poll conducted in June by Istanbul Economy Research showed 46.9 percent of respondents favored Hagia Sophia being opened to Muslim worship while 38.8 percent said it should remain a museum. Thirteen percent said it should be open to worship for all religions.