Family members rushed to be by the side of Queen Elizabeth on Thursday after doctors said they were concerned about the health of Britain's 96-year-old monarch, saying she should remain under medical supervision.
Here is some reaction to the news:
BRITISH PRIME MINISTER LIZ TRUSS
"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."
OPPOSITION LABOUR LEADER KEIR STARMER
"Along with the rest of the country, I am deeply worried by the news from Buckingham Palace this afternoon. My thoughts are with Her Majesty The Queen and her family at this time, and I join everyone across the United Kingdom in hoping for her recovery."
LEADER OF OPPOSITION LIBERAL DEMOCRATS ED DAVEY
"The whole nation's thoughts and prayers are with Her Majesty The Queen and her family as we all hope and pray for her full recovery."
FIRST MINISTER OF SCOTLAND NICOLA STURGEON
"All of us are feeling profoundly concerned at reports of Her Majesty's health. My thoughts and wishes are with the Queen and all of the Royal Family at this time."
FIRST MINISTER OF WALES MARK DRAKEFORD
"Concerned to hear the news from Buckingham Palace. I send my best wishes to Her Majesty and her family on behalf of the people of Wales."
ARCHBISHOP OF CANTERBURY JUSTIN WELBY
"My prayers, and the prayers of people across the @churchofengland and the nation, are with Her Majesty The Queen today. May God's presence strengthen and comfort Her Majesty, her family, and those who are caring for her at Balmoral."
PRESIDENT OF CATHOLIC BISHOPS' CONFERENCE OF ENGLAND AND WALES, CARDINAL VINCENT NICHOLS
"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."
SPEAKER OF PARLIAMENT LINDSAY HOYLE
"I know I speak on behalf of the entire House when I say we send all the best wishes to Her Majesty The Queen."
US AMBASSADOR TO UNITED KINGDOM JANE HARTLEY
"I join the people of the United Kingdom, the United States, and across the world in sending our thoughts and prayers to Her Majesty The Queen and her family."
COMMONWEALTH SECRETARY-GENERAL PATRICIA SCOTLAND
"Like everyone, I am deeply concerned to hear the statement from Buckingham Palace today. On behalf of every nation and citizen of the Commonwealth family, I send my best wishes to Her Majesty and the Royal Family. She will remain in my prayers."
FORMER PRIME MINISTER TONY BLAIR, VIA HIS INSTITUTE
"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."
FORMER PRIME MINISTER DAVID CAMERON
"Deeply concerned by the news this afternoon from Buckingham Palace. I send my heartfelt thoughts and prayers to Her Majesty The Queen and the Royal Family at this worrying time."