Queen Elizabeth II has decided to break with tradition and celebrate Christmas at Windsor Castle rather than at her Sandringham estate, British media reported on Monday.

The decision comes as Britain is gripped by rising numbers of cases of the Omicron variant of the coronavirus, and the possible introduction of new restrictions.

Britain's domestic Press Association news agency quoted an unnamed royal source as saying the decision "was a personal one taken after careful consideration".

The 95-year-old monarch will see family at the historic castle west of London over Christmas and "sensible precautions and all appropriate guidelines will be followed", it added.

The Queen has been forced to limit her official duties after an overnight hospital stay in October that prompted medics to advise her to rest.

Last week, she cancelled her traditional pre-Christmas family lunch for the second year in succession because of the risks of the spread of the virus.

Last year, strict rules on household mixing indoors and social distancing were in place, preventing her children, grandchildren and great-grandchildren as well as cousins from meeting.

The Queen and senior members of the royal family traditionally spend Christmas at Sandringham, in eastern England, attending church on the estate on Christmas Day.

This Christmas is the monarch's first since the death in April of her husband of 73 years, Prince Philip, Duke of Edinburgh.

Britain's Prime Minister Boris Johnson on Monday resisted calls from scientists to impose tougher restrictions on social mixing before the festive season this weekend.

Johnson, however, has said the government was keeping the situation "under constant review", as the number of positive tests nudged towards a record 100,000 a day, with a growing number from the Omicron mutation.