Video report by ITV News Washington Correspondent Robert Moore
The death of the Duke of Edinburgh at the age of 99 has sent shockwaves around the world, with tributes for Prince Philip pouring in from leaders in every corner of the globe.
British Prime Minister Boris Johnson thanked the Queen's husband for his "extraordinary life and work" in serving the UK as Britain's longest serving royal consort.
The PM said Philip would be remembered for his "steadfast support" of the Queen, as well as his awards scheme which "inspired" countless young people.
Mr Johnson's statement from Downing Street was followed by a flurry of tributes from political leaders, including the prime ministers of India, Israel and Australia.
The Duke and Duchess of Sussex have paid tribute to the Duke of Edinburgh on their Archewell website, which features the words: “Thank you for your service…You will be greatly missed”.
The site has switched to a memorial page with a dark brown background.
Meanwhile US President Joe Biden highlighted the Duke of Edinburgh’s “decades of devoted public service”.
The US president said he and wife Jill were keeping the Queen and her family “in our hearts” as he led international tributes to Philip, who died at the age of 99 on Friday.
“Over the course of his 99-year life, he saw our world change dramatically and repeatedly. From his service during World War II, to his 73 years alongside the Queen, and his entire life in the public eye — Prince Philip gladly dedicated himself to the people of the UK, the Commonwealth, and to his family,” Mr Biden said in a statement.
“The impact of his decades of devoted public service is evident in the worthy causes he lifted up as patron, in the environmental efforts he championed, in the members of the armed forces that he supported, in the young people he inspired, and so much more.
“His legacy will live on not only through his family, but in all the charitable endeavours he shaped.”
How are people marking this significant moment in royal history? ITV News Correspondent Richard Pallot reports
Barack Obama recounted how he and wife Michelle were apprehensive of the “palaces and pomp” when they visited during his time as US president, but that the Queen and Philip put them “at ease with their grace and generosity”.
“Prince Philip in particular was kind and warm, with a sharp wit and unfailing good humour. It was our first introduction to the man behind the title, and in the years since, our admiration for him has only grown. We will miss him dearly,” Mr Obama added.
The royal families of Holland and Belgium also paid condolences to their British counterparts.
King Philippe and Queen Mathilde of Belgium said they are "deeply saddened" by the Duke's death, in a tweet from their official Twitter account.
"We wish to express our deepest condolences to Her Majesty The Queen, the British Royal Family and the people of the United Kingdom," they said.
The Dutch royal family sent its "heartfelt sympathy" to the Queen, with a post from the official Twitter account of the Royal House of the Netherlands.
A a message from King Willem-Alexander, Queen Maxima and Princess Beatrix said: "His lively personality never ceased to leave an unforgettable impression.
"Our deepest and most heartfelt sympathy goes out to Her Majesty Queen Elizabeth and all the members of the Royal Family."
Australian PM Scott Morrison said the duke "embodied a generation that we will never see again".
Peter Smith reports from outside the school Prince Philip attended as a youth
"Australians send our love and deepest condolences to her Majesty and all the Royal family.
"The Commonwealth family joins together in sorrow and thanksgiving for the loss and life of Prince Philip. God bless from all here in Australia," he tweeted.
Prime minister of Canada Justin Trudeau described Philip as a "man of great purpose and conviction".
He said on Twitter: "It was with deep sadness that I learned of the passing of The Duke of Edinburgh today."
He added: "The thoughts of all Canadians are with her and the entire Royal Family as they mourn this significant loss."
Justin Welby, the Archbishop of Canterbury, said Philip was an "outstanding example of Christian service".
In a statement, he said: "On the occasions when I met him, I was always struck by his obvious joy at life, his enquiring mind and his ability to communicate to people from every background and walk of life.
"The legacy he leaves is enormous."
Indian prime minister Narendra Modi tweeted that his thoughts were with the royal family. He said: "(Philip) had a distinguished career in the military and was at the forefront of many community service initiatives. May his soul rest in peace."
European Commission president Ursula von der Leyen tweeted: "I am saddened to hear of the passing of His Royal Highness Prince Philip.
"I would like to extend my sincere sympathy to Her Majesty The Queen, the Royal Family and the people of the United Kingdom on this very sad day."
Israel's Prime Minister Benjamin Netanyahu tweeted: "I express my deepest condolences to Her Majesty Queen Elizabeth, Prince Charles, the Royal Family and the people of the United Kingdom on the passing of the Duke of Edinburgh.
"Prince Philip was the consummate public servant and will be much missed in Israel and across the world."
Ireland's Taoiseach Micheal Martin posted on Twitter: "Saddened to hear of the death of HRH Prince Philip, Duke of Edinburgh.
"Our thoughts and prayers are with Queen Elizabeth and the people of the United Kingdom at this time."
Wales First Minister Mark Drakeford offered his condolences to the Queen, saying "it is with sadness that we mourn" the Duke's death.
"We offer our sincere condolences to Her Majesty Queen Elizabeth II, his children and their families on this sad occasion," he said in a statement.
"He will be missed by the many organisations that he supported as Patron or President over many decades of service."
First Minister of Scotland Nicola Sturgeon said she was "saddened" by the news.
She sent her "personal and deepest condolences, and those of the Scottish government and people of Scotland, to Her Majesty the Queen and her family".
King Carl XVI Gustaf of Sweden said in a statement: "The Queen and I were deeply saddened to learn of the death of His Royal Highness The Duke of Edinburgh.
"Prince Philip has been a great friend of our family for many years, a relation which we have deeply valued.
"His service to his country will remain an inspiration to us all.
"We offer our sincere condolences to Her Majesty The Queen, The Royal Family and the people of the United Kingdom."