Queen Elizabeth II placed under medical supervision at Balmoral Castle; Prince Charles, Prince WIlliam rushed to her side

The UK's Queen Elizabeth has been placed under medical supervision over concerns for her health, the royal family announced on Thursday.

"Following further evaluation this morning, The Queen’s doctors are concerned for Her Majesty’s health and have recommended she remain under medical supervision," the family said in a statement.

"The Queen remains comfortable and at Balmoral (Castle)" — the Scottish estate where she has spent the summer.

She is 96 years old.

On Wednesday, the monarch canceled a meeting of her Privy Council and was ordered to rest.

Prime Minister Liz Truss, who was sworn in by the Queen on Tuesday, said she was thinking of her, in a post on Twitter,

The speaker of the British parliament said Queen Elizabeth was in the house's thoughts. "I know I speak on behalf of the entire House when I say we send all the best wishes to her Majesty the Queen," Lindsay Hoyle said in parliament.

Her eldest son and heir apparent, Prince Charles, was traveling to Balmoral, as well as his wife Camilla, and his son Prince William, officials said.

She has been suffering from "episodic mobility problems" since the end of last year and had COVID-19 in February.

The monarch, Britain's Head of State, has increasingly handed over duties to her heir, Prince Charles, and other royal family members.

She has recently missed other high-profile events, including this year's State Opening of Parliament and the Platinum Jubilee Concert.