The Latest on the death of Muhammad Ali (all times EDT):
Bill Clinton paid an emotional tribute to Mohammed Ali on social media.
The 42nd U.S. president tweeted: "Goodbye my friend. You were Great in so many ways."
Former heavyweight champion Mike Tyson also took to social media. "God came for his champion. So long great one," Tyson said in a tweet.
Madonna tweeted: "This Man. This King. This Hero. This Human! Words cannot express. He shook up the World! God Bless Him."
Muhammad Ali will be on the June 13 cover of Sports Illustrated for the 40th time in a photo shot by Neil Leifer while Ali trained in Miami Beach in 1970. "Muhammad Ali was a singular force of athletics, humanitarianism and social equality unlike anyone in our history," says group editor Paul Fichtenbaum.
President Barack Obama says Muhammad Ali "shook up the world and the world is better for it."
Obama says he keeps a pair of Ali's gloves on display in his private study, just off the Oval Office and under the famous photograph of the young champion "roaring like a lion over fallen Sonny Liston."
Obama says in a statement that Ali "fought for what was right," stood with Martin Luther King Jr. and Nelson Mandela "when it was hard" and "spoke out when others wouldn't."
Obama says even as Ali's physical powers were in decline, the boxing great "became an even more powerful force for peace and reconciliation around the world."
The president says Parkinson's disease may have "ravaged" Ali's body, but it "couldn't take the spark from his eyes."
Spectators at the English Derby, one of the biggest events in British horse racing, have
The applause took place before racing began Saturday, soon after Queen Elizabeth II arrived at Epsom racecourse.
One of Britain's top television interviewers, Michael Parkinson, had four verbal bouts opposite Ali — and described the fighter Saturday as the most memorable guest of his 40-year career.
Parkinson told the BBC that Ali's family recently asked him to provide audio recordings of all four interviews, so that Ali would listen to the decades-old discussions, which produced myriad clips highlighting his quick wit and indignation over racial discrimination.
"He was the most extraordinary man I ever met. He could be threatening. When I questioned him about his views on race, there was real anger in his response — and I looked into the eyes of somebody I thought might fell me in one blow," Parkinson said.
"That was just one aspect of a multi-faceted man and I loved him in a sense. When you look at all the thousands I've interviewed a few stand out. And he was the one that stands out most of all."
The head of the Nelson Mandela Foundation says the Nobel Peace Prize winner and former South African president called Muhammad Ali his boxing hero.
"Madiba had great respect for his legacy and spoke with admiration of Ali's achievements," Sello Hatang, the foundation's CEO, said in a statement Saturday.
A photograph of Ali and Mandela together sat next to the former president's desk at his foundation, the statement said, and Mandela's
The statement included a comment Mandela made at an event in Washington in 1990: "There is one regret I have had throughout my life: that I never became the boxing heavyweight champion of the world."
Irish President Michael D. Higgins says the people of Ireland have awoken to news of Ali's passing "with the greatest sadness."
Ireland's ceremonial head of state called Ali a man of "wit, grace and beauty" who "brought his message of freedom and respect for people of all races to all the continents of the world."
Referring to Ali's long fight against Parkinson's disease, Higgins said the boxer inspired untold millions by displaying "courage in the face of great difficulties. He was intent on communicating right to the very end."
Ireland, a nation that long has punched above its weight in the ring, has
British boxer Amir Khan has paid tribute to Ali in a video message from his family's native Rawalpindi in Pakistan.
"Muhammad Ali was my hero. I'm so happy that I got to meet the guy," said Khan, who admired every aspect of Ali's game: his unique skillset, his confidence and his faith.
"He was one of the only fighters who predicted what round he was going to win and then knock his opponent out in that round. That's something you hardly ever see."
"He used to beat opponents with his mouth before he ever got into the boxing ring. He would win the fight before the fight even happened."
Khan, a British-born Muslim, said Ali showed courage for converting to Islam in 1960s America. "What he believed in, he did."
Tributes to Muhammad Ali rolled in from around the world Saturday, just hours after his death.
"The Greatest" had been hospitalized for respiratory problems Thursday, and news spread that this illness was serious. Late Friday, his family confirmed that he had died.
Reaction came in from around the world of sports, entertainment and politics. President Bill Clinton who awarded Ali the Presidential Citizens Medal, mourned the death of the three-time heavyweight champion.
"Hillary and I are saddened by the passing of Muhammad Ali," Clinton said in a statement. "From the day he claimed the Olympic gold medal in 1960, boxing fans across the world knew they were seeing a blend of beauty and grace, speed and strength that may never be matched again."
A memorial service is scheduled for 10 a.m. in Louisville, Kentucky, Ali's hometown.