The president of Turkey has controversially declared the Hagia Sophia, a historic house of worship in Turkey, will open to Muslim worship after a court decision ruled it's conversion to a museum was illegal.

Turkish president Recep Tayyip Erdogan made the decision within an hour of a Turkish court condemned modern Turkey's founding statesman's move to turn the place of worship into a museum, Aljazeera reports.

International warnings did not advise the change of status for the iconic building.

What is Hagia Sophia? Now known as the Mosque of Hagia Sophia, the historic place of worship in Istanbul, was formerly known as the Church of Hagia Sophia. It has served in many capacities, including a Greek Orthodox Christian patriarchal cathedral, a Roman Catholic cathedral, an Ottoman mosque, and a secular museum.

The house of worship was built between 532 and 537 AD during Roman emperor Justinian I's reign as the cathedral church of Constantinople. At the time, it was the worlds largest interior space.

ision of Turkey's president, who has been accused by the Russian Orthodox Church of ignoring the voices of millions of Christians.

"The concern of millions of Christians has not been heard," says Vladimir Legoida, a spokesperson for the Russian Orthodox Church.

Legoida says the court ruling shows that "all calls for the need for extreme delicacy in this matter were ignored."

Orthodox Christian leader Ecumenical Patriarch Bartholomew has previously stated the conversion of the Istanbul monument would disappoint Christians and "fracture" the East and West.

UNESCO is calling on Turkish authorities to "open a dialogue without delay in order to avoid a step back from the universal value of this exceptional heritage."

The United Nations' cultural body says their World Heritage Committee will review the Hagia Sophia's status during its next session and called the Turkish decision "regrettable," a sentiment echoed by the European Union's foreign policy chief Josep Borrel.

A State Department spokesperson for the United States says they are "disappointed" by the Turkish government's decisions on the matter.

Countries including Greece and Cyprus also have decried Erdogan's decision.