Buckingham Palace says Queen Elizabeth II has died at age 96. The monarch was under medical supervision Thursday as doctorswere "concerned for Her Majesty’s health.

"The Queen died peacefully at Balmoral this afternoon," the palace tweeted. "The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow."

Earlier Thursday, the palace said the queen was “comfortable” and remained at Balmoral Castle in Scotland, where she spent the summer, and family members canceled long-planned engagements to travel to the Highlands.

A fleet of cars carrying Prince William, Prince Andrew, Prince Edward and his wife Sophie, the Countess of Wessex, arrived at Balmoral Castle about an hour after their plane landed in Aberdeen, Scotland.

Prince Harry, who was due to appear at a charity awards ceremony in London later Thursday, canceled that appearance and made his way to Scotland separately. He was photographed arriving at Balmoral on Thursday evening without Duchess Meghan, who their spokesperson previously confirmed would join him.

Duchess Kate did not join her husband, William, either – Thursday was their children's first day of school outside of London, about an eight-hour drive from Balmoral

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Prime Minister Liz Truss said "the whole country will be deeply concerned by the news from Buckingham Palace this lunchtime." "My thoughts — and the thoughts of people across our United Kingdom — are with Her Majesty The Queen and her family at this time," she said on Twitter.

Canada's Prime Minister Justin Trudeau also shared his thoughts for the queen. "My thoughts, and the thoughts of Canadians across the country, are with Her Majesty Queen Elizabeth II at this time. We’re wishing her well, and sending our best to the Royal Family," he tweeted.