Turkish president Tayyip Erdogan has declared Istanbul’s Hagia Sophia open to Muslim prayer as a mosque after a top court ruled that the building’s conversion to a museum in 1934 was illegal.

Mr Erdogan made his announcement just an hour after the court ruling was revealed, brushing aside international warnings not to change the status of the nearly 1500-year-old monument that is revered by Christians and Muslims alike.

The Turkish leader used a televised speech Friday to urge people to respect the decision.

The Hagia Sophia will open for Friday prayers on July 24, Mr Erdogan said.

“Since its status as a museum is changed, we are cancelling the entrance fees,” he said.

“Like all our mosques, its doors will be open to everyone – Muslim or non-Muslim. As the world’s common heritage, Hagia Sophia with its new status will keep on embracing everyone in a more sincere way.”

“We will be treating every opinion voiced on the international stage with respect. But the way Hagia Sophia’s will be used falls under Turkey’s sovereign rights. We deem every move that goes beyond voicing an opinion a violation of our sovereignty,” Mr Erdogan said.

The United States government and church leaders were among those to express concern about changing the status of the UNESCO World Heritage Site, a focal point of both the Christian Byzantine and Muslim Ottoman empires and now one of the most visited monuments in Turkey.

UNESCO said it deeply regretted Turkey’s decision, lamenting a lack of dialogue prior to the decision on the status of the former Byzantine cathedral.

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Greece’s culture ministry described the court decision as an “open provocation” to the civilised world.

But Mr Erdogan has sought to shift Islam into the mainstream of Turkish politics in his 17 years at the helm.

He has long proposed restoring the mosque status of the huge sixth-century building, which was converted into a museum in the early days of the modern secular Turkish state under Mustafa Kemal Ataturk.

“The decision was taken to hand over the management of the Ayasofya Mosque… to the Religious Affairs Directorate and open it for worship,” the decision signed by Erdogan said.

The Council of State, Turkey’s top administrative court, said in its ruling: “It was concluded that the settlement deed allocated it as a mosque and its use outside this character is not possible legally.

“The cabinet decision in 1934 that ended its use as a mosque and defined it as a museum did not comply with laws,” it said, referring to an edict signed by Mr Ataturk.

The association which brought the court case, the latest in a 16-year legal battle, said Hagia Sophia was the property of the Ottoman leader who captured the city in 1453 and turned the already 900-year-old Greek Orthodox cathedral into a mosque.

Mr Erdogan, a pious Muslim, threw his weight behind the campaign before local elections last year which dealt a painful blow to his ruling Islamist-rooted AK Party.

The Ottomans built minarets alongside the vast domed structure, while inside they added huge calligraphic panels bearing the Arabic names of the early Muslim caliphs alongside the monument’s ancient Christian iconography.

The Russian Orthodox Church said it regretted that the court did not take its concerns into account when making its ruling and said the decision could lead to even greater divisions, the TASS news agency reported.

-with agencies