Vatican City, Holy See: People donned Santa caps on beaches, ski slopes and streets around the globe on Monday to celebrate Christmas, as Pope Francis called for an end to the wars in Gaza and Ukraine that this year has cast a shadow over one of the world's favourite holidays.

In his annual Christmas Day "Urbi and Orbi" mass at the Vatican, Pope Francis called for an end "to war, to every war, to the very mindset of war, an aimless voyage, a defeat without victors, an inexcusable folly".

May peace "come in Israel and Palestine, where war is devastating the lives of those peoples", he said.

"I reiterate my urgent appeal for the liberation of those still being held hostage. I plead for an end to the military operations with their appalling harvest of innocent civilian victims, and call for a solution to the desperate humanitarian situation by an opening to the provision of humanitarian aid", he said.

"I implore peace for Ukraine. Let us renew our spiritual and human closeness to its embattled people", he said, also calling for the resolution of conflicts simmering in the Middle East, Africa and the Caucasus.

The Gaza war made for a sombre Christmas in Bethlehem, the biblical city in the occupied West Bank where Christians believe Jesus Christ was laid in a manger after being born more than 2,000 years ago.

The town did away with its giant Christmas tree, marching bands and flamboyant nativity scene that normally draw tourists, settling for just a few festive lights.

In the centre of town, a huge Palestinian flag had been unfolded with a banner declaring that "The bells of Bethlehem ring for a ceasefire in Gaza".

"A lot of people are dying for this land," said Nicole Najjar, an 18-year-old student.

"It's really hard to celebrate while our people are dying."

Inside Gaza, the horrid conditions were driving "rising desperation due to acute hunger,"  World Health Organization chief Tedros Adhanom Ghebreyesus said on Monday.

The Gaza war started after a Hamas attack on October 7 left around 1,140 people dead in Israel, most of them civilians. The Palestinian militants also abducted around 250 people, 129 of whom Israel says remain in Gaza.

Israel retaliated with a sustained bombardment and ground invasion of Gaza, that has killed more than 20,400 people, mostly women and children, according to Gaza's health ministry.

New Christmas Day
Ukraine, invaded by Russia nearly two years ago, this year is celebrating Christmas on December 25 for the first time, jettisoning the traditional Orthodox date of January 7, which is feted in Russia.

"We believe that we really should celebrate Christmas with the whole world, far away, far away from Moscow. For me that's the new message now," said one smiling parishioner in Odesa, Olena, whose son is a medic on the front line.

The date change -- moving away from the Julian calendar favoured by the Orthodox Church -- is part of numerous moves since the invasion to remove traces of the Russian and Soviet empires.