Britain's King Charles III called for "compassion and reconciliation" at a time of "division" across the world in his Christmas Day message on Thursday.

The 77-year-old monarch said he found it "enormously encouraging" how people of different faiths had a "shared longing for peace".

Charles praised individuals who risked their lives to save others in situations of violence, including those caught up in the killings at a Jewish event at Bondi Beach in Australia this month.

"Individuals and communities have displayed spontaneous bravery, instinctively placing themselves in harm's way to defend others," said the king whose words were accompanied by images of events at Bondi.

Eighty years after the end of World War II, the king said the courage of servicemen and women and the way communities came together after the conflict carried "a timeless message for us all".

Charles did not make any reference to his battle with cancer, nor did he mention his younger brother Andrew who in October was stripped of his royal titles over his links to convicted US sex offender Jeffrey Epstein.

The message did feature images of his son and heir Prince William, as well as his grandson George.

The Christmas song that ended the message was sung by a Ukrainian choir formed after the start of the conflict with Russia in 2022.

The king and other members of the royal family, including Andrew's daughters, attended a Christmas service at St Mary Magdalene Church on Charles's private Sandringham estate in Norfolk. (AFP)