The 74-year-old sports icon, born Cassius Clay, passed away on 3 June (16), days after being admitted to a medical centre in Phoenix, Arizona, for respiratory complications.

Reports suggest he spent his final few hours on life support, and a family spokesman has since been revealed Ali, who battled Parkinson's disease, died of septic shock.

Famous fans have continued to flock to social media to offer their condolences and memories of the legendary boxer, who called himself The Greatest Of All Time (G.O.A.T.).

President Obama - who keeps a pair of Ali's boxing gloves on display in his private office at the White House - and his wife Michelle released a touching statement on Saturday (04Jun16), honouring his legacy.

"Muhammad Ali was The Greatest. Period. If you just asked him, he'd tell you. He'd tell you he was the double greatest; that he'd 'handcuffed lightning, thrown thunder into jail,'" they wrote.

"But what made The Champ the greatest - what truly separated him from everyone else - is that everyone else would tell you pretty much the same thing. Like everyone else on the planet, Michelle and I mourn his passing. But we're also grateful to God for how fortunate we are to have known him, if just for a while; for how fortunate we all are that The Greatest chose to grace our time...

"Muhammad Ali shook up the world. And the world is better for it. We are all better for it. Michelle and I send our deepest condolences to his family, and we pray that the greatest fighter of them all finally rests in peace."

Obama later took to Twitter to echo the sentiments he shared in his statement, and simply wrote, "We pray that the greatest fighter of them all finally rests in peace."

Further tributes have also come from stars including Lionel Richie and Paul MCCartney.

"You will always be my hero... #MuhammadAli," Richie wrote on, while MCCartney shared memories of meeting the boxer on his website, accompanied by a picture of the Beatles when they met Ali back in the 1960s.

"Dear Muhammad Ali. I loved that man. He was great from the first day we met him in Miami, and on the numerous occasions when I ran into him over the years," the singer recalled.

"Besides being the greatest boxer, he was a beautiful, gentle man with a great sense of humour who would often pull a pack of cards out of his pocket, no matter how posh the occasion, and do a card trick for you. The world has lost a truly great man. Love Paul."

Meanwhile, Jamie Foxx was spotted leaving a Hollywood nightclub on Friday wearing a T-shirt emblazoned with "Muhammad Ali: People's Champ", and a bright blue bomber jacket with "Cassius Clay" on the back, and Usher also sported a simple T-shirt tribute to Ali as he headlined the 9th Annual Roots Picnic festival in Philadelphia, Pennsylvania on Saturday (04Jun16).

A private memorial service for the fighter is set to be held in his hometown of Louisville, Kentucky, on Thursday (09Jun16), while a public funeral will take place at the KFC YUM! Center sports arena on Friday (10Jun16), when Billy Crystal, who performed at Ali's retirement bash in 1979, will be joined by Clinton and sports presenter Bryant Gumbel to deliver eulogies. The ceremony will take place following a procession of Ali's body through the city for members of the public to pay their final respects.