Thousands of people came together across creeds and nationalities for a Muslim prayer service in remembrance of Muhammad Ali on Thursday, the start of a two-day farewell to the beloved boxing legend and civil rights hero.

Men, women and whole families filled the cavernous Freedom Hall arena in Ali's hometown in Kentucky to pay their respects before the casket of the 20th century's most singular personalities, who died last week at age 74.

The brief ceremony in Louisville launched two days of interfaith tributes, bringing together dignitaries and ordinary fans, honoring a man known for both his tenacity in the ring and his social activism outside of it.

"It was fabulous, seeing all the different nationalities, cultures, races, religions come together, even though it's a very sad situation that he passed, it's very inspirational," said Makeeba Edmund, a city employee, who is Muslim.

Muslim men and women prayed in separate rows, most of the latter with their heads veiled.

One of those paying his respects was Babacar Gaye, a 54-year-old native of Senegal who remembers watching Ali fights at a house in Dakar as a teenager.

"There would be at least 60 people watching it on a small black and white television," Gaye told AFP.

Born Cassius Clay at a time of racial segregation in the American South, the boxer converted to Islam in 1964, changing his name to Muhammad Ali and shocking America.

Thursday's prayer service was held at the site of Ali's last fight in his hometown, where he defeated Willi Besmanoff on November 29, 1961.

The three-time heavyweight world champion died after a decades-long battle with Parkinson's disease.

- 'Live his legacy' -

"Muhammad Ali has a very, very special significance for the Muslim community," Imam Zaid Shakir, who helped organize the prayer service, said earlier.

"This is about... sending him off in the very best of fashion," said the Muslim cleric, adding that Ali would want his supporters to "honor his memory, live his legacy and love each other."

For millions of Muslims around the world, Ali symbolized the true face of Islam, promoting peace and tolerance.

Semsudin Haseljic comes from a small village in central Bosnia and resettled in Louisville after being injured in the war in 1993. He remembers how the whole community would gather for Ali's fights -- typically broadcast at around 4 am -- in one of the two houses in the village with a television set.

"We had one of our elders who pretty much knew all of his fights by heart," said the 54-year-old. "At that time there was not much entertainment in the community, so people who gather and ask him: 'Come on, narrate the fights'."

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On Friday morning, a funeral procession will wind through the city of 600,000, passing sites that were important to Ali: his childhood home, the Ali Center, the Center for African American Heritage -- which focuses on the lives of blacks in Kentucky -- and, of course, along Muhammad Ali Boulevard before arriving at the cemetery for a private burial.

Actor Will Smith -- who earned an Oscar nomination for his portrayal of Ali on the silver screen -- and former heavyweight champion Lennox Lewis will be among the pallbearers.

An anonymous individual has pledged to cover the path to the grave with red rose petals.

Friday afternoon, Ali will be honored at an interfaith memorial service at a large sports arena that will bring together heads of state, VIPs and fans alike.

More than 15,000 people are expected to attend -- with free tickets to the memorial service given out in a half-hour and a black market for the coveted tickets sprouting online.

Former president Bill Clinton and comedian Billy Crystal will eulogize Ali, while Turkish President Recep Tayyip Erdogan will be in attendance.

Barack Obama will not be attending the funeral of the man he calls a "personal hero" since it coincides with his daughter Malia's graduation.

But the president Thursday published a video message in which he displayed two mementoes gifted to him by "The Champ" -- a book of photographs and a set of gloves -- and which have accompanied him through his time in the White House.

"This week we lost an icon," Obama said in the Facebook message. "A person who for African Americans, I think, liberated their minds in recognizing that they could be proud of who they were."

"I grew up watching him. I grew up having my identity shaped by what he accomplished," he said.

"The incredible gestures of love and support that he showed me, was one of the great blessings of my life."