HM The Queen is said to be under medical supervision at Balmoral following concern from doctors for her health.
Members of the Royal Family are said to be on their way, or already at the Scottish estate. Prince Charles and the Duchess of Cornwall have travelled to Balmoral, while the Duke of York and the Count and Countess of Wessex are on their way.
Also travelling to Balmoral are the Duke of Cambridge and the Duke and Duchess of Sussex. The Duchess of Cambridge is staying at home with their children.
"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 from Buckingham Palace said.
It added that the Queen is comfortable.
Just two days ago she was pictured meeting the new Prime Minister, Liz Truss to appoint her to the role. She said that the country would be “deeply concerned” by the news.
"My thoughts - and the thoughts of people across our United Kingdom - are with Her Majesty The Queen and her family at this time," she added.
Political leaders in Northern Ireland have been sending their best wishes to the Queen. DUP leader Sir Jeffrey Donaldson and UUP leader Doug Beattie both said their thoughts and prayers are with the Queen, while Alliance leader Naomi Long sent her best wishes.
Sending best wishes to HMT Queen for a full and swift recovery and thoughts with members of the Royal Family who are concerned for her health at this time.— Naomi Long MLA (@naomi_long) September 8, 2022
Meanwhile, the Archbishop of Armagh, John McDowell, said he "and the people of the Church of Ireland, conscious of concerns around the health of Her Majesty Queen Elizabeth, would offer their prayers and urge others to pray at this very difficult time".
The Moderator of the Presbyterian Church in Ireland, Right Reverend Dr John Kirkpatrick said, “Along with many across these islands and those in our Church, I was deeply concerned to hear the news from Balmoral regarding the Queen’s health.
"Praying for Her Majesty and her family at this very anxious time, as many across our denomination will be. Praying that she will experience the presence of The Lord, and strong faith in weakness. May she also know rest and the Lord’s hand upon her. Grace and peace be with her family.”