Pope Francis is focusing his attention on all those weeping in the world this Christmas, singling out the refugees, hostages and all those suffering in conflicts in the Middle East, Africa and Ukraine.

On a day that brings joy to little ones in much of the world, Pope Francis expressed anguish for children who are victims of violence, including the recent terrorist attack on a Pakistani military school, or those who are trafficked or forced to be soldiers.

Tens of thousands of Romans and tourists in St Peter's Square listened as the Pope delivered the Catholic church's traditional "Urbi et Orbi" (Latin for "to the city and to the world") Christmas message from the central balcony of St Peter's Basilica.

Pope Francis said: "Truly there are so many tears this Christmas."

Pope Francis began his review of the world's troubled places by recalling the persecution of ancient Christian communities in Iraq and Syria, along with those from other ethnic and religious groups.

"May Christmas bring them hope," he said.

Referring to refugees and exiles, he prayed: "May indifference be changed into the necessary humanitarian help to overcome the rigours of winter."

The Pope also thanked those courageously helping people infected with Ebola in Africa.

He prayed, too, that those in affluent countries, who are "immersed in worldliness and indifference," will experience a softening of heart.