Turkey’s president, Recep Tayyip Erdoğan, has led worshippers in the first prayers in Istanbul’s iconic Hagia Sophia since his controversial declaration that the monument, which over the centuries has served as a cathedral, mosque and museum, would be turned back into a Muslim house of worship. The Turkish leader and an entourage of senior ministers arrived for the service in the heart of Istanbul’s historic district on Friday afternoon, kneeling on new turquoise carpets while sail-like curtains covered the original Byzantine mosaics of Jesus and the Virgin Mary. Erdoğan began the service with a recital from the Qur’an before the head of Turkey’s religious authority, Ali Erbas, continued the formal prayers for hundreds of specially invited attendees while the call to prayer rang out from the building’s minarets. “This is Hagia Sophia breaking away from its chains of captivity. It was the greatest dream of our youth,” Erdoğan said before the reopening. “It was the yearning of our people and it has been accomplished.” Outside, in Sultanahmet Square, about 350,000 people joined the president in worship. Many had arrived on buses from all over the country the night before, camping on the square overnight. Hundreds of excited people pushed past police crowd control lines on Friday morning, eager to be a part of the historic occasion. “I’m very very happy,” said Abdulazim Gassama, a theology student from Mali living in Turkey. “African Muslims know about the Hagia Sophia, Constantinople and Byzantium. This is important for Islam.” In neighbouring Greece, scenes of an opposite nature unfolded: bells tolled and flags flew at half-mast at hundreds of churches across the country in protest at the move, and Orthodox church leaders held vigils describing Friday as a “day of mourning”. The Unesco-listed Hagia Sophia (Divine Wisdom), known in Turkish as Ayasofya, was completed in AD537 by the Byzantine emperor Justinian. After the Ottoman conquest of Constantinople in AD1453 Sultan Mehmet II converted it into an imperial mosque, adding four minarets around the building’s grand central dome. Mustafa Kemal Atatürk, the secular founder of the Turkish Republic, turned the Hagia Sophia into a museum in 1934 in a symbolic break with the past, but Turkish Islamists and nationalists have campaigned for decades to restore its Muslim heritage. A Turkish court paved the way for the Hagia Sophia’s newest chapter after it ruled unanimously this month to annul Atatürk’s decision. Erdoğan. who has championed Islamic values during his 17 years in office, signed a presidential order turning the site back into a mosque almost immediately. The move appears to be designed to please his ruling Justice and Development party’s conservative voter base as the government struggles to shore up popular support amid a burgeoning economic crisis. Leading opposition figures have for the most part refused to engage in Turkey’s latest polarising political issue, either ignoring the Hagia Sophia decision or offering muted support. Internationally, however, the monument’s rebirth as a mosque has been greeted with dismay, drawing criticism from the US secretary of state, Mike Pompeo, Pope Francis and several Orthodox church leaders around the world. The Hagia Sophia has also further strained relations between Ankara and Athens, which are at a low ebb over migrant flows and oil and gas drilling rights in the Mediterranean. “Today is a difficult day ... a shadow hangs over us with the transformation of Hagia Sophia into a mosque, something that genuinely shocks Christians all over the world and not only Greeks,” the Greek government spokesperson, Stelios Petsas, said in an interview with private channel Open TV. “We have warned for some time that this will create an unbridgeable gap between Turkey and the Christian world.” Erdoğan has brushed off the international criticism, claiming the Hagia Sophia’s future is an issue of national sovereignty – a favourite topic for the populist president. Osman Tarhan, a mechanic, was among the crowds singing and waving Turkish flags outside the 1,500-year-old building on Friday. “I see the condemnation from the Christian world as meaningless. Muslims prayed inside for five centuries, and there are a lot of churches converted from mosques in Spain. These things happen,” the 45-year-old said. “The story of the Hagia Sophia mosque didn’t end in the 1930s. That was only a break, and now it is a mosque again.”