Thousands of mourners paid a final tribute on Wednesday to the life of Rosa Parks, a humble seamstress who, with once act of defiance, helped transform a country.

"She did help to set us all free," said former U.S. president Bill Clinton in his tribute to the woman credited with sparking the civil rights movement nearly 50 years ago.

Clinton is among the 4,000 mourners who honoured the memory of the civil rights pioneer at her funeral, which followed a week of remembrances during which her coffin was taken from Detroit to Montgomery, Ala., were she refused to give up her seat to a white man on a Montgomery city bus on Dec. 1, 1955.

"I remember as it if it were yesterday, that fateful day 50 years ago. I was a nine-year-old Southern white boy who rode on a segregated bus every single day of my life," Clinton said.

It was after Parks refused to give up her seat that Clinton and his two friends decided they wouldn't sit in the front anymore.

"It was just a tiny gesture by three ordinary kids. But that tiny gesture was repeated over and over again, millions and millions of times, in the hearts and minds of children, their parents, their grandparents, their great-grandparents," Clinton said.

Clinton was the first of some three dozen clergy, politicians, business and civic leaders who spoke at the funeral, held at Detroit's Greater Grace Temple.

Those in the audience at the packed church held hands and sang the civil rights anthem, "We Shall Overcome," as family members filed past her casket before it was closed in the funeral's first hour.

Bishop Charles Ellis III led the service. "Mother Parks, take your rest. You have certainly earned it," he said.

"The woman we honoured today held no public office, she wasn't a wealthy woman, didn't appear in the society pages," said U.S. Senator Barack Obama.

"And yet, when the history of this country is written, it is this small, quiet woman whose name will be remembered long after the names of senators and presidents have been forgotten."

Hours before the service began, the line to get one of the 2,000 available public seats extended more than two blocks west of the church.

Already, at least 60,000 have paid tribute to Parks as she lay in honour in Montgomery, in the Capitol Rotunda in Washington, and her adopted city of Detroit.

At a three-hour memorial service Monday at historic Metropolitan A.M.E. Church in Washington, TV host Oprah Winfrey, who was born in Mississippi during segregation, said Parks changed the course of history.

Her stand "changed the trajectory of my life and the lives of so many other people in the world," Winfrey said.

Parks was 92 when she died in Detroit on Oct. 24.

On Dec. 1, 1955, Parks was a 42-year-old tailor's assistant when she was arrested and fined $10 US plus $4 in court costs for refusing to give up her seat.

Her historic stand against segregation prompted a 381-day boycott of the bus system led by the Rev. Martin Luther King Jr.

The U.S. Supreme Court vindicated Parks in 1956, ruling that segregation on municipal bus systems was unconstitutional.

Despite the legal victory, both Parks and her husband Raymond faced harassment and death threats in Montgomery, where they also lost their jobs.

They moved to Detroit with Parks' mother, Leona McCauley, in 1957.

In 1987, Parks co-founded a nonprofit group, the Rosa and Raymond Parks Institute for Self Development, to help Detroit's youth develop leadership skills and awareness of the importance of civil rights.