Pope Francis has urged the world's 1.2 billion Catholics to feel compassion for children, notably victims of war, migration and homelessness in his Christmas Eve mass but also those "not allowed to be born".
Addressing a 10,000-strong crowd, the pontiff urged worshippers to celebrate "authentically", by acknowledging "the fragile simplicity of a small newborn" and "the tender affection of the swaddling clothes".
"Let us allow the child in the manger to challenge us, but let us also allow ourselves to be challenged by the children of today's world," he said, speaking in St Peter's Square.
Many children have died this year while attempting the perilous Mediterranean migrant crossing to Europe which has claimed more than 5,000 lives in 2016 alone.
Thousands of Syrians including children meanwhile left the former rebel enclave of Aleppo this week after four months of suffocating siege.
Children are "hiding underground to escape bombardment" or "on the pavements of a large city, at the bottom of a boat overladen with immigrants", the pontiff said, before reiterating his opposition to abortion.
"Let us allow ourselves to be challenged by the children who are not allowed to be born, by those who cry because no one satiates their hunger, by those who do have not toys in their hands, but rather weapons," he said.
And in an echo of his well-established criticisms of materialism, Francis also urged the faithful to avoid indifference, "when Christmas becomes a feast where the protagonists are ourselves, rather than Jesus".
Pope Francis will deliver his fourth Christmas message at St Peter's Square tomorrow.
Crowds gather in Bethlehem for midnight mass
Crowds gathered in Bethlehem for Christmas Eve celebrations ahead of midnight mass, with more visitors expected than in 2015 due to a drop in violence.
People flocked to Manger Square, near the Church of the Nativity, built over the spot where tradition says Mary gave birth to Jesus.
Some snapped selfies near the square's giant Christmas tree and watched the annual Scouts parade in the city, located a short drive from Jerusalem in the Israeli-occupied West Bank.
The Scouts marched waving flags, banging drums and playing bagpipe music.
Bethlehem: Five points about the holy city
Palestinian security forces were deployed in areas leading up to the church and square, conducting searches of some people.
Christmas carols in Arabic rang out from speakers.
Archbishop Pierbattista Pizzaballa, apostolic administrator of the Latin Patriarch of Jerusalem, later arrived to cheering crowds.
The Latin Patriarchate of Jerusalem heads the Roman Catholic Church in the Holy Land.
Celebrations in Bethlehem culminated with midnight mass at the Church of the Nativity.
Some 2,500 tickets are usually given out for the mass and those wishing to attend must register in advance. Attendees usually include Palestinian officials and foreign dignitaries.
Beyond that, tens of thousands of tourists are expected to visit sites including Bethlehem, Jerusalem and Nazareth over the holidays, tourism officials say.
Israel's tourism ministry said some 120,000 visitors were expected in December, half of them Christians.
Palestinian officials said they were expecting more visitors than last year, with major hotels in Bethlehem booked.
