Buckingham Palace said on Thursday that Queen Elizabeth II is under medical supervision at her summer residence in Scotland after doctors raised concerns about the health of the 96-year-old queen, as members of the royal family rushed to stand by her side.

The palace announcement came a day after the queen canceled a virtual meeting of the Privy Council when doctors advised her to rest following a full day of events on Tuesday, when she officially asked Liz Truss to become the Prime Minister of Britain.

A palace spokesman, speaking on condition of anonymity in line with customary policy, said: "After further assessment this morning, the queen's doctors are concerned about Her Majesty the Queen's health and have recommended that she remain under medical supervision. The queen is still comfortable and at Balmoral."

The palace refused to give further details about the queen's condition, but there were worrying indications that it might be serious. A minister in Truss's cabinet interrupted during a debate in the House of Commons to inform her of Elizabeth's condition, while family members canceled long-planned commitments to travel to the Highlands.

Members of the royal family flew to Scotland, where Prince William, Charles's eldest son, was among those on their way to Balmoral, along with his brother, Prince Harry, and Harry's wife, Meghan.

The gathering also comes at Windsor Castle just three months after people across Britain paused during a long weekend to celebrate the 70th anniversary of the queen's accession to the throne. While crowds of fans cheered and waved flags in the streets around Buckingham Palace throughout four days of celebrations, the queen only appeared twice on the palace balcony to wave to them. Elizabeth has increasingly delegated duties to Charles and other members of the royal family in recent months as she recovered from a COVID-19 bout, began using a cane, and struggled to get around.

Political leaders from various spectrums joined Truss in expressing their concern, and the Archbishop of Canterbury, Justin Welby, said the "nation's prayers" were with Elizabeth.

Since ascending to the throne after her father's death on February 6, 1952, Elizabeth has been a symbol of stability as Britain negotiated the end of the empire, the dawn of the information age, and mass immigration that transformed the country into a multicultural society.

Throughout her reign, the queen also built a relationship with the people of Great Britain through an apparently endless series of public appearances where she opened libraries and hospitals, and awarded honors to deserving citizens.

Deborah Langton (67), a semi-retired translator, outside Buckingham Palace said: "I don't know exactly about her health condition, but I have a feeling, somehow, that we might be ready for something. And if this is, you know, the end, it will be very sad, I think, for a long time."