"Let us say once more a firm and clear 'No!' to every form of violence, vengeance and hatred carried out in the name of religion or in the name of God," the Pope said in Italian in a speech at a peace conference at Al-Azhar University, the premier seat of high learning among Sunni Muslims.
Francis met with Sheikh Ahmed el-Tayeb and became the first pontiff to visit the institution since Pope John Paul II in 2000.
The Pope and the Grand Imam spoke at the closing of the International Conference for Peace, organized by Al-Azhar. When he greeted the Grand Imam, the Pope called him "my brother." The men sat side by side at the conference.
The roots of extremism
The Pope's visit comes nearly two weeks after the Palm Sunday bombing of two Coptic churches,
brazen strikes that left at least 45 people dead
. He addressed a familiar theme: the roots of violent extremism.
Francis opened his speech with "As-Salaam Alaikum," the traditional Muslim greeting in Arabic that means "Peace be upon you," after the imam's address.
"In order to prevent conflicts and build peace, it is essential that we spare no effort in eliminating situations of poverty and exploitation where extremism more easily takes root, and in blocking the flow of money and weapons destined to those who provoke violence," he said.
Francis called for an end to the "proliferation of arms" and lambasted "demagogic forms of populism."
"If they are produced and sold, sooner or later they will be used," he said. "Only by bringing into the light of day the murky maneuverings that feed the cancer of war can its real causes be prevented. National leaders, institutions and the media are obliged to undertake this urgent and grave task."
El-Tayeb addressed the status of faith in modern life.
"With all these accomplishments [of the 21st century], how come peace has become a lost paradise? The answer, I assume, is that modern civilization has ignored religion," he said.
The Pope was greeted earlier in the day on the tarmac at Cairo International Airport by Egyptian Prime Minister Sherif Ismail, Egyptian state TV showed.
He then was received by Egyptian President Abdel-Fattah al-Sisi around 2:30 p.m. (8:30 a.m. ET), at the Ittihadiya Presidential Palace in Cairo. The leaders stood shoulder to shoulder as the pontifical and Egyptian national anthems played.
"An integral part of this country"
After the peace conference, the Pope and the Egyptian President arrived at Al-Masa Hotel and addressed religious and political dignitaries.
The Pope, again speaking in Italian, focused on Egypt's role in fighting terrorism in the region, evoking incidents from its biblical and modern history. He ceremonially greeted all Egyptian people, including minority Christians -- Coptic Orthodox, Greek Byzantines, Armenian Orthodox, Protestants and Catholics.
"Your presence in this, your country, is not new or accidental, but ancient and an inseparable part of the history of Egypt," he said. "You are an integral part of this country, and over the course of the centuries you have developed a sort of unique rapport, a particular symbiosis, which can serve as an example to other nations."
Francis highlighted the sacrifice of members of the army and the police, the forced exodus of Christians from Sinai and the latest church bombings. He also stressed respect for human rights and religious freedoms.
"Egypt thus has a singular task, namely, to strengthen and consolidate regional peace even as it is assaulted on its own soil by senseless acts of violence," he said.
He gave several nods to Egypt in Arabic, mentioning the motto of the 1952 Revolution: "al-din lillah wal watan liljami" -- "Religion belongs to God and the nation to all"; he ended his speech with, "Shukran wa tahya misr!" -- "Thank you and long live Egypt!"
Visit with the Coptic Pope
Pope Tawadros II, head of Egypt's Coptic Orthodox Church, then greeted Francis at St. Mark's Coptic Orthodox Cathedral in Cairo's Abbassiya district, state TV said. They walked together in procession and took part in ecumenical prayers at the adjacent church of St. Peter, the site of a deadly blast in December
that left at least 23 people dead.
Francis commended the efforts of Tawadros II, whom he called a brother, in organizing meetings between the Coptic Orthodox and Catholic churches.
"It is a promising sign that the following meeting took place this year in Rome, as if to bespeak a particular continuity between the Sees of Mark and Peter," he said, referring to the apostles of Jesus Christ credited with founding the churches.
Francis and Tawadros II signed a joint, 12-point declaration reiterating the fraternity between their churches. "Let us intensify our unceasing prayer for all Christians in Egypt and throughout the whole world, and especially in the Middle East," the declaration states.
"The tragic experiences and the blood shed by our faithful who were persecuted and killed for the sole reason of being Christian, remind us all the more that the ecumenism of martyrdom unites us and encourages us along the way to peace and reconciliation," it reads.
Francis planned to return Friday night to the papal ambassador's residence, where he is staying. After dinner, he's due to appear outside the residence to bless 300 children who are on a pilgrimage across Egypt.
The Pope is expected to celebrate Mass on Saturday in Cairo and visit Egypt's small Catholic community.