In Turkey, the iconic Hagia Sophia in Istanbul has reopened for the first day of Muslim prayers after its conversion back into a mosque. President Recep Tayyip Erdogan took part in Friday's worship. Earlier this month, a top Turkish court ruled that the Hagia Sophia had been illegally made into a museum 86 years ago. Erdogan then ordered the building to be restored as a mosque. The monument is cherished by both Muslims and Christians, and the move has raised concerns with Christian church leaders and officials in the US, Greece, and Russia. UNESCO has stated the changes may have to be reviewed by its World Heritage Committee. Turkey says the site will remain open to visitors outside of prayer hours and its Christian artworks will be protected.