Balmoral, UK - The UK's Queen Elizabeth II is under medical supervision at Balmoral with doctors concerned for her health, Buckingham Palace has said.

The monarch (96) pulled out of a virtual Privy Council on Wednesday, a day after appointing Liz Truss as prime minister during a meeting at the queen's home in the Scottish Highlands.

A palace spokesperson said: "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 queen remains comfortable and at Balmoral."

The queen's close family, including Prince Charles, have been informed, with the latest announcement escalating fears for the monarch's health.

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Prime Minister Liz Truss said "the whole country will be deeply concerned by the news from Buckingham Palace this lunchtime," adding, "My thoughts – and the thoughts of people across our United Kingdom – are with her majesty the queen and her family at this time."

The nation's longest-reigning monarch has ongoing mobility issues and looked bright but frail and used a walking stick during Tuesday's historic audience with Truss, which followed a visit from outgoing prime minister Boris Johnson as he tendered his resignation.