In one of the most moving tributes, Nelson Mandela said that he and fellow South Africans were "devastated" by the news. "I had the honour of hosting her a few months ago and was tremendously impressed by her. She was undoubtedly one of the best ambassadors for Great Britain," he said.
"I found her very grateful, highly intelligent and committed to worthy causes and was tremendously impressed by her warmness."
"We liked her very much. We admired her work," Bill Clinton said. "For myself, I will always be glad that I knew the princess and always think of her in very strong and positive terms, as will Hillary."
He sent a message of condolences that sounded more than usually heartfelt. "I know that this is a very difficult time for millions of people in the United Kingdom, who are deeply shocked and grieving, and the American people send their condolences. We value their friendship and we understand this great and painful experience," he said.
President and Mrs Clinton were told while they were at a beach party. They embraced and were visibly shaken, a spokesman said, then settled in front of a television set with other party guests to watch breaking news coverage. They left the party soon afterwards.
Russia's President Boris Yeltsin also expressed his deep sorrow. "The President of the Russian Federation B.N. Yeltsin is deeply shocked by the news from Paris of the tragic loss of Princess Diana," said a statement from the Kremlin. "She was well known and loved by the Russian people. All know of Princess Diana's big contribution to charitable work, and not only in Great Britain," it said.
There was deep regret in Australia from republicans and royalists alike. "On behalf of the Australian government and the Australian people I want to extend my very deep sympathy, particularly to her two young sons who have suffered the trauma of a marriage break-up and have now lost their mother at the very young age of 36," said Australian Prime Minister John Howard.
The Princess had done much to keep the monarchy's image youthful and contemporary in Australia, a country where republicanism has made great strides in recent years. ABC television scrapped its Sunday afternoon programme schedules and replaced them with a live satellite broadcast of BBC television from Britain, an interruption unheard-of in Australia, even for grave international political crises.
Many paid tribute to her humanitarian role. Imran Khan, a close friend of the Princess, said she had left a legacy of service to the needy. She "achieved unprecedented heights in the service of mankind," he said. Diana visited Pakistan in May to help Imran Khan and his wife, Jemima Goldsmith, raise more than $12m for the Shaukat Khanum Memorial Cancer Hospital.
French President Jacques Chirac said: "It is with tremendous emotion that I learn of the brutal loss of Lady Diana. She was a young woman of our time, warm, full of life and generosity. Her tragic death will be profoundly felt because she was a familiar figure to everyone."
Several politicians commented caustically on the press pursuit of Diana, which precipitated her death.
Germany's Chancellor Helmut Kohl called Diana "the victim of an evermore brutal and unscrupulous competition of a part of the media. This terrible accident and her death should finally give those responsible in the media a reason to reflect."
In Sweden, the spokeswoman for the royal household, Elisabeth Tarras- Wallberg, said: "When you literally chase someone to death to make money from pictures, things have gone too far." The Danish Foreign Minister Niels Helveg Petersen also criticised the media. "The bottom line must have been reached for what photographers can do," he said.
The simplest, and one of the most direct, tributes came from Italian opera star Luciano Pavarotti. "My heart is full of grief and pain," he said in a statement. "Lady Diana was the most beautiful symbol of humanity and love for all the world. She touched my life in an extraordinary way ... she can never be replaced and I will always remember her with deep love and joy."