From the White House to Kinshasa and Uzbekistan they remembered on Saturday a sporting and cultural icon, saying there would never be another one like Muhammad Ali, "The Greatest".
 
Ali was recalled not just as a heavyweight boxing king but also for his fight for social justice, while others told moving personal stories of his warmth and generosity, how he was equally at home with presidents and people on the streets.

President Barack Obama hailed Ali, who died on Friday after a long battle with Parkinson's Disease, as a towering champion "who fought for what was right".

"His fight outside the ring would cost him his title and his public standing," Obama said in a heartfelt statement.

"It would earn him enemies on the left and the right, make him reviled, and nearly send him to jail. But Ali stood his ground and his victory helped us get used to the America we recognise today."

Ali had been Nelson Mandela's hero, the Nelson Mandela Foundation said, revealing how Mandela's favourite book at his office was an autographed copy of an Ali biography and that there was a photo of the two men together there.

"Nelson Mandela, a boxing enthusiast most of his life, acknowledged Ali as his boxing hero. Madiba had great respect for his legacy and spoke with admiration of Ali's achievements," said Sello Hatang, chief executive of the foundation.

Reflecting Ali's reach far beyond boxing, former US president Bill Clinton said he had been "honoured" to award Ali the Presidential Citizens Medal at the White House in January 2001, just before leaving office.

"Through triumph and trials", Clinton said, Ali "became even greater than his legend".

Thousands of kilometres away in Kinshasa, underlining Ali's enduring global appeal, they still talk about that historic night in 1974 in what was then Zaire -- the "Rumble in the Jungle".

Ali knocked out the previously undefeated George Foreman in the greatest victory of his storied career.

"Ali was part of our youth, it is he who shaped us," Martino Kavuala, a former amateur boxer now aged 63, remembered fondly.

"In those days, if you were young and you didn't box, it wasn't only that you weren't really a youngster, you didn't have a place in society."

  

- 'My idol, my hero' -

Football great Pele led the tributes from the sporting world, which united to remember one of its biggest names.

"The sporting universe has just suffered a big loss. Muhammad Ali was my friend, my idol, my hero," Pele said on Instagram.

"We spent many moments together and always kept a good connection throughout the years. The sadness is overwhelming."

Ali spoke out for African-American civil rights in the 1960s, carrying on his fight against injustice and sacrificing the prime years of his own career in the process.

Retired NBA all-time scoring leader Kareem Abdul-Jabbar praised Ali's courage in fighting discrimination.

"At a time when blacks who spoke up about injustice were labelled uppity and often arrested, Muhammad willingly sacrificed the best years of his career to stand tall and fight for what he believed was right," said Abdul-Jabbar.

"In doing so, he made all Americans, black and white, stand taller. I may be 7-feet-2 but I never felt taller than when standing in his shadow."

Ali won an Olympic gold medal in 1960 and battled the onset of Parkinson's to light the torch at the 1996 Olympic opening ceremony in one of the most memorable moments in Games history.

Thomas Bach, president of the International Olympic Committee, said Ali "was engaged beyond sport, an athlete who had the courage to give hope to so many suffering illness by lighting the Olympic cauldron and not hiding his own affliction".

  

- Boxing tributes -

Foreman reminisced about the three-way rivalry he enjoyed with Ali and Joe Frazier during heavyweight boxing's most feted era, tweeting: "Ali, Frazier and Foreman... we were one guy. A part of me slipped away, the greatest piece."

"We lost a legend, a hero and a great man," said Floyd Mayweather, who retired last year as an unbeaten welterweight champion. "He's one of the guys who paved the way for me to be where I'm at. Words can't explain what Muhammad Ali did for the sport."

Another former world heavyweight title-holder, Mike Tyson, tweeted: "God came for his champion. So long great one. The Greatest. RIP."

Don King, who promoted the Rumble in the Jungle, said Ali will live on forever alongside other US civil rights heroes.

"He was tremendous, not just a boxer, a great human being, an icon," King said. "Muhammad Ali's spirit, like Martin Luther King Jr., will live on. That's why Muhammad Ali will never die."

In Tashkent, Uzbekistan at the amateur World Series of Boxing the crowd and boxers from Cuba and Britain stood in respectful silence as three bells rang out in poignant respect. (AFP)