Queen Elizabeth II dies 'peacefully'; Prince William, Harry arrive at Balmoral Castle

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."

The announcement on Thursday comes a day after Queen Elizabeth canceled a meeting of her Privy Council and was told to rest. 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.

Here's a timeline of updates from the palace and members of the royal family leading up to the queen's death.

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Princes William and Harry, other royal family members travel to be with queen

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.

King Charles along with his wife, Queen Consort Camilla, and sister, Princess Anne, arrived earlier Thursday.

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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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New Prime Minister Liz Truss sends thoughts

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.

Truss was interrupted during a debate in the House of Commons to be informed about Elizabeth’s condition Thursday.

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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.

Others offering thoughts and prayers included U.S. Ambassador to the U.K. Jane Hartley and Archbishop of Canterbury Justin Welby.

Queen Elizabeth II to skip beloved Highland Games event due to continuing 'mobility' issues

Queen postponed Privy Council meeting, advised to rest

The latest announcement comes a day after Buckingham Palace revealed Queen Elizabeth II postponed a meeting of senior governmental advisers known as the Privy Council after doctors advised her to rest.

The council had been scheduled to meet virtually on Wednesday, a day after the monarch had a full day of activities as she presided over the ceremonial handover power to the new prime minister at her summer residence in Scotland.

Truss would have taken the oath as First Lord of the Treasury, one of her other titles, and new Cabinet ministers would have been sworn in during the session. The meeting will be rescheduled.

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Queen Elizabeth underwent recent mobility issues

The queen increasingly handed over duties to King Charles and other members of the royal family in recent months as she struggled to get around.

The queen's latest postponement comes days after she decided to skip the Braemar Gathering, a popular Highland Games event she loves and attends every year, as she continues to struggle with issues getting around.

Last week, the monarch also decided to formally appoint Britain's new prime minister on Tuesday at Balmoral Castle rather than make the more than 800-mile round trip to London for the traditional ceremony at Buckingham Palace.

Her eldest son and heir King Charles, who normally accompanied the monarch to the Highland Games, attended in her stead.

Contributing: Naledi Ushe, Amy Haneline, USA TODAY; The Associated Press 

This article originally appeared on USA TODAY: Queen Elizabeth II updates: Monarch dies following doctors concerns