Queen Elizabeth under medical supervision: Doctors concerned; children by her side [details]

Queen Elizabeth, 96, is under medical supervision after doctors were concerned for her health. A statement from Buckingham Palace said in a statement that the queen is comfortable at Balmoral Castle in Scotland. The Queen hasn't been hospitalised. 

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

Prince Charles has travelled to Balmoral to visit the Queen amid health concerns. All her four children are said to be with the queen at Balmoral Castle along with her grandson Duke of Cambridge. 

Citing the Queen's health concerns, the traditional ceremony of the Changing of the Guard, which was to take place on Friday outside Buckingham Palace, has been called off.

People are wishing the Queen a speedy recovery, as many have shared their messages on social media. 

"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," Prime Minister Liz Truss tweeted.

Ex-UK PM Tony Blair said he was 'deeply concerned' over Queen's health. 

"It is deeply concerning to hear today's news from Buckingham Palace. My thoughts and prayers are with Her Majesty the Queen and her family at this worrying time," Blair said.

"I am concerned to hear the news about the Her Majesty The Queen's health. I offer my prayers for her and her family. May the blessings of the Lord strengthen and comfort her and her family," Archbishop of Westminster said. 

The announcement by Buckingham Palace comes a day after the Queen cancelled a meeting of her Privy Council and was asked to rest. The Queen had presided over the ceremonial handing of power to the new PM Liz Truss on Tuesday at Balmoral.

Queen Elizabeth II is the longest-serving monarch of the UK. She has already named her successor to be Prince Charles, who is handling many of the queen's duties alongside other members of the royal family.

This is a developing story...