A sombre Pope Francis steeped his Christmas message to the world today in sadness for those with little cause
for joy — abused children, refugees, hostages, and others suffering from violence in the Middle East, Africa, Ukraine and elsewhere.

Anguish for children who suffer maltreatment or violence, including in the recent attack on a Pakistani military school, tempered the pontiff's traditional Christmas Day speech, which he delivered from the central balcony of St. Peter's Basilica in Rome.

A crowd, estimated by the Vatican to number more than 80,000 Romans, tourists and pilgrims, filled St. Peter's Square for the "urbi et orbi" message (Latin for "to the city and to the world").

"Truly there are so many tears this Christmas," said Francis, looking solemn and smiling little, in contrast to his often jocular demeanour when addressing crowds.

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Pope Francis kisses a woman with her child as he leads the Christmas night mass in Saint Peter's Basilica at the Vatican. (Max Rossi/Reuters)

He lamented that many children are "made objects of trade and trafficking" or forced to become soldiers, as well as those never born because of abortion.

"I think also of those infants massacred in bomb attacks, also those where the Son of God was born," said Francis, referring to the Middle East.

Francis decried the persecution of ancient Christian communities in Iraq and Syria, at the hands of ISIS militants, 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 closeness, and rejection into hospitality." He expressed hope they'd receive humanitarian help to withstand the "rigours of winter, return to their countries and live with dignity."

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

In his litany of the world's troubled places, he denounced hostage-taking in Nigeria, and hoped that reconciliation would prevail over "hatred and violence" in Ukraine, where pro-Russian rebels have been fighting against government forces in the east of that country.

While much of his message concerned poor countries, Francis had harsh words for some in affluent nations. He prayed for an end to the hardened hearts "of so many men and women immersed in worldliness and indifference, the globalization of indifference."

Christmas joy will only be realized when weapons are transformed "into ploughshares, destruction into creativity, hatred into love and tenderness," Francis concluded before giving the crowd his blessing.

About an hour after the Pope went inside, a protester from the Femen activist group bared her chest and snatched the statue of Baby Jesus in the life-sized nativity scene at the centre of the square, while thousands of visitors were strolling across the space. A gendarme from the Vatican's security forces hustled away the woman, after she was covered with a coat.