Buckingham Palace says the Queen is being monitored by medics at Balmoral after they started to worry about her health.

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

"The Queen remains comfortable and at Balmoral."

Her immediate family has been informed.

The announcement comes after the Queen, 96, pulled out of a virtual Privy Council on Wednesday, with doctors advising her to rest.