Nelson Mandela's tearful widow was among scores of mourners who paid their last respects before his open casket Wednesday, as the much-loved leader lay in state.

Graca Machel, clad in a black head-dress with her eyes shielded by sunglasses, placed both hands on the raised coffin before turning away disconsolate.

At each end of the coffin stood two navy officers clad in white dress uniform, heads bowed, eyes closed and swords pointing downward.

Later, presidents, royalty and thousands of South Africans made their own pilgrimage.

Some stopped briefly to pray, others bowed or brushed against the rope balustrade to get a closer look at the mortal remains of a man who had earned a place in history long before his demise.

Some collapsed, felled by the weight of their grief, before being helped away by medical personnel or fellow onlookers.

A blind man with a cane passed by, helped by an aide.

"I was just feeling sad when I saw him lying there as if he can wake up. As if I can say 'Mr Mandela, how are you?" said 44-year-old Anna Mtsoweni, who waited in line from 5:00 am.

Among the dignitaries were Mandela's former political foe FW de Klerk, ex-wife Winnie Madikizela-Mandela and musician and activist Bono.

The Irish rocker accompanied Mandela's long time aide-de-camp Zelda Le Grange, who appeared heartbroken and needed to be supported throughout.

Public guard of honour

Earlier a black hearse flanked by 16 motorcycle outriders had carried Mandela's flag-draped coffin on a solemn journey through the streets of Pretoria, the South African capital.

The cortege moved briskly through streets lined with flag-waving South Africans who formed a public guard of honour.

"I never met Mandela, so this is my only chance and it's important I pay my respects. I'm South African -- I have to be here," said 28-year-old Vaughan Motshwene.

Some cheered but many were tearful, aware that Mandela's death on Thursday aged 95, opened a new chapter in South African history.

"It feels like the end of an era. All the opportunities I've had growing up that my parents never had, Madiba gave me that," said government employee Faaiqia Hartley, 27.

"He gave all of us an opportunity to be the best we could be."

At Union Buildings, the seat of South African government, the casket was unloaded by eight pallbearers representing the branches of the armed forces in full uniform.

From there it was carried up the steps toward the towering acropolis of beige freestone, where nearly two decades ago Mandela was sworn in as the country's first black president, signifying the rebirth of this long-troubled nation.

Trailing behind the coffin was Mandela's oldest grandson, Mandla Mandela, his manifest grief a poignant reminder that while the nation lost a hero, Mandela's family lost a father, grandfather and husband.

Mandela's open coffin was placed on a cubic platform in the building's amphitheatre, soon to be renamed in his honour, where it will be on view for three days.

Journey of memories

Mandela's final journey through Pretoria is laden with symbolism and replete with landmarks that carry resonance in his life and that of this deeply scarred nation.

The procession passed the central prison where he was jailed in 1962 for incitement and leaving the country illegally.

Another landmark is the Palace of Justice, the court where Mandela famously stood trial in 1963-64 for treason and sabotage with 10 other codefendants.

His conviction and subsequent life sentence marked the beginning of a 27-year jail stint, from which he finally emerged in 1990 as the structure of apartheid crumbled around its white minority supporters.

The cortege will pass near the one-time home of Paul Kruger, the father of the Afrikaner nation.

"Oom (Uncle) Paul" was the president of the Transvaal, leading a resistance movement against British rule during the first Anglo-Boer War, which began in 1880.

That Afrikaner nationalism later morphed into support for the National Party, which introduced apartheid.

The funeral procession will be repeated for three days, ending each time at the Union Buildings where previous presidents signed aspects of the apartheid system into law.

The public will be allowed to view the casket each afternoon, before Mandela's body is transported to his boyhood home of Qunu in the Eastern cape for its eventual burial on Sunday.

The lying in state was a sombre, subdued affair compared to Tuesday's celebratory memorial service in Soweto -- the crucible of the anti-apartheid movement.

Tens of thousands of people attended the event in Soweto's World Cup stadium where US President Barack Obama led foreign tributes to the life and legacy of Mandela, whose appeal and influence spread far beyond his native land.

Mandela had been critically ill for months, but the announcement of his death was still a body blow to a country struggling with multiple social and economic challenges.

For many, Mandela -- even a frail, aged and retired Mandela -- represented, while alive, a moral beacon.

Current President Jacob Zuma was roundly booed by large portions of the crowd at Tuesday's memorial service, a sign of growing impatience with Mandela's successors to deliver on promises of equality and prosperity.