Pope Francis, the leader of the world's 1.2 billion Catholics, has visited a landmark mosque in Istanbul in a gesture of respect to Islam as he visits Turkey.
During his November 29 visit to Sultan Ahmet mosque, popularly known as the Blue Mosque, he closed his eyes and engaged in a moment of apparent reflection as he stood alongside the grand mufti of Istanbul, Rahmi Yaram, who performed an Islamic prayer.
He later visited Hagia Sophia, which in the course of some 15 centuries of history has served as a church, a mosque, and now a museum.
The Argentine-born pontiff was on the second day of a trip to Turkey aimed at fostering better interfaith relations to counter the rise of fundamentalism and terrorism.
His visit is seen as a crucial test of his ability to build bridges between faiths amid the rampage by Islamic State (IS) jihadists in Iraq and Syria and concerns over the persecution of Christian minorities in the Middle East.
Francis also met in Istanbul on November 29 with the Ecumenical Patriarch of Constantinople, Bartholomew I, who is the spiritual leader of the world's 300 million Orthodox Christians.
The pope arrived in Istanbul from Ankara, where he met with Turkish leaders, and called for religious tolerance and peace in the Middle East.
Speaking on November 28 after meeting Turkey's top cleric Mehmet Gormez in Ankara, Francis called the situation in Iraq and Syria "particularly tragic."
"Everyone suffers the consequences of these conflicts and the humanitarian situation is unbearable," he said. "I think of so many children, the suffering of so many mothers, of the elderly, of those displaced, and of all refugees, of every type of violence."
The pope also deplored the fact that communities are being targeted simply because of their beliefs.
"Of particular concern is the fact that, owing mainly to an extremist and fundamentalist group, that entire communities, especially -- though not exclusively Christians and Yazidis -- have suffered and continue to suffer barbaric violence simply because of their ethnic and religious identity," he said.
He also said that "fanaticism and fundamentalism, as well as irrational fears which foster misunderstanding and discrimination, need to be countered by the solidarity of all believers" and that it is "essential that all citizens, Muslim, Jewish, and Christian…enjoy the same rights and respect."
In Istanbul on November 29, the pontiff celebrated mass in the Catholic Cathedral of the Holy Spirit, in front of a congregation that was expected to include Christian refugees from Iraq.
Iraq's Christian population has fallen by nearly 70 percent since the start of its 2003 war. Syria's total Christian minority made up around 10 percent of the population of 22 million before its civil war began in 2011.
Turkey's own Christian community is tiny -- just 80,000 in a country of some 75 million Muslims -- but extremely mixed, consisting of Armenians, Greek Orthodox, Franco-Levantines, Syriac Orthodox, and Chaldeans.
Of these only the small Franco-Levantine and Chaldean communities regard the pope as the head of their churches.
Bartholomew I, who leads the Ecumenical Patriarchate of Constantinople, extended a warm welcome to Francis upon his arrival in Istanbul.
"Your Holiness, beloved brother in Christ, we welcome you with great joy, esteem, and love. Blessed is he who comes in the name of the Lord," Bartholomew said.
The two church leaders presided over an ecumenical prayer service at the Orthodox patriarchate on November 29, the eve of the feast of St. Andrew, the patron saint of the Orthodox world.
The Ecumenical Patriarchate of Constantinople is one of 14 autocephalous (self-led) churches that make up Orthodox Christianity, and Bartholomew frequently acts as an intermediary between Orthodox and other Christian believers, including Catholics and Protestants.
The patriarchate is considered the "first among equals" among the 14 Orthodox churches because of its historical location in what was the capital of the former Eastern Roman Empire, or Byzantium. However, it does not exercise control over the other individual churches and is dwarfed in size by the Russian Orthodox Church, the largest Orthodox congregation in the world.