Muhammad Ali has been laid to rest.

A private service was held for family and close friends at A D Porter & Sons funeral home hours earlier, and thousands of fans lined the streets as a procession of black Cadillacs followed the car carrying Ali's body in a cherry red coffin, which was draped with an Islamic shroud, through the town.

The procession took the same route the legendary boxer's victory parade did in 1960, when he celebrated winning a gold medal at the Rome Olympics.

The town's mayor, Greg Fischer, hopes the public turnout gave the sporting legend the "class, dignity and respect" he deserved.

He said: "We've all been dreading the passing of the champ, but at the same time we knew ultimately it would come.

"It was selfish for us to think that we could hold on to him forever. Our job now, as a city, is to send him off with the class and dignity and respect that he deserves."

US President Barack Obama will miss the public service, but he and wife Michelle have sent a letter to be read during the ceremony. Instead, white House senior adviser Valerie Jarrett - who knew Ali personally - will represent the President.

But the politician has praised the boxer as an "icon and a personal hero" in a video message.

He said: "It's very rare when a figure captures the imagination of the entire world. It's even rarer when that figure does so by being open and funny and generous and courageous.

"He was one of a kind. In my book, he'll always be the greatest."

At the funeral service, which is currently believed to be running around an hour later than planned, former US President Bill Clinton will deliver a eulogy while comedian Billy Crystal and sports journalist Bryant Gumbel are also expected to speak.

Ali planned the details of his funeral, which will be an interfaith memorial service in the Muslim tradition, in keeping with his beliefs.