"So many other footsteps are hidden in the footsteps of Joseph and Mary," the Argentine pontiff, himself the grandson of Italian migrants, told worshippers at Christmas Eve mass in Saint Peter's Basilica.
"We see the tracks of millions of persons who do not choose to go away but, driven from their land, leave behind their dear ones."
Many engulfed in the ongoing migration crisis were forced to flee from leaders "who, to impose their power and increase their wealth, see no problem in shedding innocent blood", said the 81-year-old.
The pontiff's plea for "hope" came as fresh tensions simmered in the West Bank following President Donald Trump's recognition of Jerusalem as Israel's capital. Following Trump's lead, Guatemala's President Jimmy Morales said Sunday his country would move its embassy from Tel Aviv to Jerusalem.
Trump's announcement on December 6 unleashed demonstrators and clashes, including in Bethlehem in the Israeli-occupied West Bank where Christians marked the birth of Jesus at a midnight mass.
Fewer tourists in Bethlehem
Celebrating midnight mass in the ancient town, Archbishop Pierbattista Pizzaballa, apostolic administrator of the Latin Patriarch of Jerusalem, used his homily to lambast the wars that "the Herods of today fight every day to become greater, to occupy more space".
He urged "Christians of the Holy Land, who are worried, and perhaps afraid by the reduction of our numbers, the inadequacy of our means, the insecurity that characterises our daily life," to have courage in the troubled region.
Criticising Trump's announcement, Pizzaballa insisted "Jerusalem is a city of peace, there is not peace if someone is excluded. Jerusalem should include, not exclude," stressing the principle that Jerusalem is a city for both peoples and the three Abrahamic faiths.
"Jerusalem is our mother," he said, and if one of her children "is missing the mother cannot be at peace, so we have to pray for the peace of Jerusalem," the archbishop said in his homily in the presence of Palestinian president Mahmoud Abbas.
Trump's decision to recognise Jerusalem as the capital of Israel has sparked almost daily protests in the Palestinian territories and put a damper on Christmas festivities.
Palestinian scouts played drums and bagpipes at celebrations in Bethlehem, but many tourists stayed away.
Hundreds gathered in the cold on Bethlehem's Manger Square to watch the annual scout parade towards the Church of the Nativity, built over the spot where tradition says Mary gave birth to Jesus.
But the square was noticeably quieter following the violence between Palestinian protesters and the Israeli army in the past weeks.
Twelve Palestinians have been killed since Trump's declaration, including a 19-year-old who died of his wounds on Sunday nine days after he was shot during a Gaza protest.
In the square, Nahil Banura, a Christian woman from Beit Sahur near Bethlehem, said Trump's decision had made the run-up to Christmas "miserable".
"People are only going out to vent," she said.
'Sadness and joy'
The Israeli army officer in charge of the Bethlehem area said that while tensions had been high in the area following the Jerusalem announcement, he did not expect trouble at Christmas.
"We've reinforced our troops, and are ready for any scenario," Lieutenant Colonel Benny Meir told AFP.
Israel seized east Jerusalem in the 1967 Middle East war and later annexed it, in moves never recognised by the international community.
Palestinians view east Jerusalem as the capital of their future state, and interpreted Trump's statement as rejecting their right to a capital in east Jerusalem, although the Americans deny this.
In a statement earlier, Abbas called on "world Christians to listen to the true voices of the indigenous Christians from the Holy Land... that strongly rejected the US recognition of Jerusalem as Israel's capital".
Mitri Raheb, pastor of the Evangelical Lutheran Christmas Church in Bethlehem, told AFP that Christmas this year is a "mix of sadness and joy" because of the US decision on Jerusalem, which he called "the beating heart of Palestine".
Christmas in Mosul
Christmas decorations have meanwhile become more visible in Christian areas of Syria's capital Damascus this year.
In the central Syrian city of Homs, Christians will celebrate Christmas with great fanfare for the first time in years after the end of battles between regime and rebel forces -- with processions, shows for children and even decorations among the ruins.
In Iraq too, this year marks a positive turning point for the Christian community in the northern city of Mosul.
Hymns filled a Mosul church on Sunday as worshippers celebrated Christmas for the first time in four years after the city's recapture from the Islamic State group in July.
Meanwhile a tragic Christmas weekend in the Philippines was compounded Monday by the deaths of 20 people killed in a bus collision while travelling to mass.
Dozens of people were feared killed in a fire Saturday in the southern city of Davao. Thousands were displaced by floods and landslides from a storm that also killed more than 200 others on Friday.