(AFP) - Pope Francis ushered in Christmas celebrations for the world's 1.3 billion Catholics on Tuesday, saying the celebration of Jesus's birth reminded humanity how "God continues to love us all, even the worst of us".

The pontiff told crowds gathered at the Vatican for his Christmas Eve Mass: "You may have mistaken ideas, you may have made a complete mess of things, but the Lord continues to love you."

Thousands of Palestinians and foreigners converged in the biblical town of Bethlehem, revered by Christians as the birthplace of Jesus, in the Israeli-occupied West Bank.

A few hundred worshippers gathered in the church on the site of Jesus's birth for midnight mass, attended by Palestinian president Mahmud Abbas. Hundreds more gathered outside, watching on screens in the crisp air.

At midnight bells rang out throughout the town, before Archbishop Pierbattista Pizzaballa, the most senior Roman Catholic official in the Middle East, led hymns and said prayers.

"At Christmas all the world looks to us, to Bethlehem," he said.

"Special greetings to our brothers and sisters in Gaza, with whom I celebrated Christmas two days ago," he added.

Pizzaballa, who had to cross Israel's separation barrier to get from Jerusalem to Bethlehem, said after his arrival that it was a difficult time but there was reason for hope.

"We see in this period the weakness of politics, enormous economic problems, unemployment, problems in families," he said.

"On the other side, when I visit families, parishes, communities, I see a lot of commitment... for the future. Christmas is for us to celebrate the hope."

Earlier in the evening, a few thousand people watched in the winter sun as Palestinian scouts paraded in front of a giant Christmas tree.

"The church is beautiful and it puts what we know in the Bible (in) place," said Laneda, an American tourist visiting the site. "Everything is just very meaningful."

- 'Bumpy year' -

The first church was built on the site of Jesus's birth in the fourth century, though it was replaced after a fire in the sixth century.

This year celebrations were bolstered by the return of a wooden fragment believed to be from the manger of Jesus.

Sent as a gift to Pope Theodore I in 640, the piece had been in Europe for more than 1,300 years before being returned last month, Francesco Patton, chief custodian for the Holy Land, said.

"We venerate the relic because (it) reminds us of the mystery of incarnation, to the fact that the son of God was born of Mary in Bethlehem more than 2,000 years ago," Patton told AFP at the time.

In the square by the church, Palestinian tourism minister Rula Maayah told AFP it had been a good year, with 3.5 million tourists visiting the city.

But fewer Christians from the Gaza Strip were in attendance than in previous years, as Israel had granted permits to just around 300 of the some 900 people who applied, said Wadie Abunassar, an adviser to Church leaders in the Holy Lan.

The Palestinian territories of the West Bank and Gaza are separated by Israeli land and crossing between them requires hard-to-get permits.

In her traditional Christmas Day message, Britain's Queen Elizabeth II was to describe 2019 as "quite bumpy" after a year of crises in the royal family.

In France, travellers were meanwhile facing more woe in the bitter nearly-three week strike by train drivers fighting government pension reform plans.

The walkout has ruined Christmas travel plans for tens of thousands of French ticket holders unable to reach loved ones in time for Christmas Day.

And French Catholics endured a sad moment as Notre-Dame Cathedral in Paris was unable to hold Christmas Eve Mass for the first time since 1803 -- after a fire ravaged its structure in April.

Worshippers instead gathered at another church a few hundred metres away.

"It isn't the same feeling but it's still a Christmas Mass," said 16-year-old Juliette, who had made the 700-kilometre trip from Aix with her family. "There will be a thought for Notre-Dame tonight, that's for sure."

A frantic scramble for gift promotions left a dozen people injured in an Australian shopping centre.

But in Hong Kong chaos broke out in an upscale shopping centre after pro-democracy protesters planned a series of Christmas Eve demonstrations.

And in the central Philippines, where Christmas is widely celebrated among the country's Catholics, thousands of people were warned to leave their homes as a severe tropical storm approached.

© Agence France-Presse