About 10,000 people attended the Christmas Eve mass at the Vatican on Saturday.
Pope Francis urged the world’s 1.2 billion Catholics to feel compassion for children in his message to the faithful massed in St. Peter's Square.
"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," the pope said.
Thousands of children have died this year while attempting the perilous Mediterranean immigrant crossing to Europe. And thousands of traumatised Syrian children were forced to leave the former rebel enclave of east 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.
He also reiterated 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.