VATICAN CITY -- Pope Francis issued a Christmas Day prayer that recent U.N.-backed peace agreements for Syria and Libya will quickly end the suffering of their people, denouncing the "monstrous evil" and atrocities they have endured and praising the countries that have taken in their refugees.

Speaking from the central balcony of St. Peter's Basilica, Francis issued a plenary indulgence for Catholics in hopes of spreading the church's message of mercy in a world torn by war, poverty and extremist attacks. The sun-soaked St. Peter's Square was under heavy security, as it has been since the Nov. 13 Paris attacks by Islamic extremists that left 130 dead.

An indulgence is an ancient church tradition related to the forgiveness of sins. Francis announced it after delivering his annual "Urbi et Orbi (To the city and the world)" speech listing global hotspots and his prayers for an end to human suffering.

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Francis referred to the "brutal acts of terrorism" that struck the French capital this year as well as attacks in Egypt's airspace, in Beirut, Mali and Tunisia. He denounced the ongoing conflicts in Africa, the Middle East and Ukraine and issued consolation to Christians being persecuted for their faith in many parts of the planet.

"They are our martyrs of today," he said.

In an indirect reference to the Islamic State of Iraq and Syria (ISIS), he said: "May the attention of the international community be unanimously directed to ending the atrocities which in those countries, as well as in Iraq, Libya, Yemen and sub-Saharan Africa, even now reap numerous victims, cause immense suffering and do not even spare the historical and cultural patrimony of entire peoples."

Francis said he hoped the plenary indulgence he issued for this, his Holy Year of Mercy, would encourage the faithful "to welcome God's mercy in our lives, and be merciful with our brothers to make peace grow."

"Only God's mercy can free humanity from the many forms of evil, at times monstrous evil, which selfishness spawns in our midst," he said.

Libya has been in a state of lawlessness since dictator Moammar Gadhafi was overthrown in 2011. Syria has seen a five-year war that has killed over 250,000 people and forced millions to flee the country. The surge of refugees flowing out of Syria to Europe has created a migration crisis for the entire continent.

"We pray to the Lord that the agreement reached in the United Nations may succeed in halting as quickly as possible the clash of arms in Syria and in remedying the extremely grave humanitarian situation of its suffering people," he said. "It is likewise urgent that the agreement on Libya be supported by all, so as to overcome the grave divisions and violence afflicting the country."

The pope called to mind the suffering of refugees and migrants fleeing their troubled homes, as well as others victimized by violence and greed. "Even today great numbers of men and women are deprived of their human dignity and, like the child Jesus, suffer cold, poverty, and rejection," he said. "May our closeness today be felt by those who are most vulnerable, especially child soldiers, women who suffer violence, and the victims of human trafficking and the drug trade."

Francis praised both individuals and countries that have taken in refugees fleeing "inhuman conditions," saying their generosity had helped the newcomers "build a dignified future for themselves and for their dear ones, and to be integrated in the societies which receive them."