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

Red and white Santa outfits appeared on surfers from Australia to Florida, on cyclists in the smog-filled streets of New Delhi and intrepid souls braving chilly Channel waters for a holiday dip near Britain's Dover.

Pope Francis deplored the desperate humanitarian situation of Palestinians in besieged Gaza and called for an immediate ceasefire and the freeing of hostages in his Christmas message.

"My heart grieves for the victims of the abominable attack of 7 October, and I reiterate my urgent appeal for the liberation of those still being held hostage," the 87-year-old said in his traditional Urbi et Orbi message.

"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 told thousands of faithful gathered at Saint Peter's Square in the Vatican.

Israel has launched a relentless bombardment and ground invasion since October 7 in Gaza, where more than 20,000 people have been killed, mostly women and children, according to the latest toll from the Palestinian Health Ministry.

Here's a glimpse of Christmas celebrations around the world.