Pope Francis condemned human “hunger for wealth and power” at Christmas Eve Mass in the Vatican.
“How many wars have we seen!” he said, adding that the main victims were “the weak and the vulnerable”.
“I think above all of the children devoured by war, poverty and injustice,” the pontiff added.
He was addressing worshippers at St Peter’s Basilica in Vatican City.
Francis, 86, entered the church in a wheelchair and sat at the site of the altar for most of the Mass on Saturday evening.
“While animals feed in their stalls, men and women in our world, in their hunger for wealth and power, consume even their neighbours, their mothers and sisters,” he said.
On Sunday, Francis is due to deliver his traditional Urbi et Orbi (to the city and the world) blessing and message from St Peter’s Basilica’s balcony to Catholics in the square below and around the world.
In the UK, the Archbishop of Canterbury, Justin Welby, is expected to say that despite war and conflicts around the world, as well as the cost of living crisis at home, there is “unconquerable hope” in the birth of Jesus Christ.
Reflecting on his recent visit to Ukraine, and looking ahead to his forthcoming visit to South Sudan with the Pope and the Moderator of the Church of Scotland, the leader of the worldwide Anglican Communion is also expected to appeal to the leaders of both South Sudan and Russia to bring an end to violence and “bring hope to millions”.