Tens of thousands of South Africans have joined dozens of world leaders for the national memorial service for former President Nelson Mandela.
The service is being held in front of a vociferous crowd in the FNB stadium in Johannesburg.
US President Barack Obama said Mr Mandela was a “giant of history”, adding: “The world thanks you for sharing Nelson Mandela with us”.
The former South African president died last Thursday, aged 95.
The country is observing a series of commemorations leading up to the funeral on Sunday.
‘A mighty life’
The memorial service is one of the biggest gatherings of international dignitaries in recent years.
There had been fears people would be turned away, but the heavy rain left areas of the 95,000 capacity stadium empty.
The service began about an hour late, with the singing of the national anthem.
Introducing the proceedings, the master of ceremonies, Cyril Ramaphosa, said that Mr Mandela’s “long walk is over… and he can finally rest”. Interfaith prayers were then held.
The first speaker, friend and fellow Robben Island inmate Andrew Mlangeni, said Mr Mandela had “created hope when there was none”.
Three of Mr Mandela’s grandchildren then delivered eulogies.
In his address, UN Secretary General Ban Ki-moon said there was “sorrow for a mighty loss and celebration of a mighty life”.
He said: “South Africa has lost a hero, it has lost a father… He was one of our greatest teachers. He taught by example. He sacrificed so much and was willing to give up all he had for freedom and democracy.”
Many people stood in the rain waiting for several hours to get into the stadium, the BBC’s Pumza Fihlani reports from the scene.
She says the crowds are in high spirits – singing and dancing, stomping their feet – and the stadium has the feel of a political rally.
Rather than seeing the rain as a dampener, many in South Africa have welcomed it.
Defence Minister Nosiviwe Mapisa-Nqakula said: “It’s a blessing from the ancestors welcoming a son of the soil.”
One of those attending, Shahida Rowe from Johannesburg, told the BBC: “The core of Mandela’s life was humanity. That is why I am here today and the world is celebrating.
“Thanks to him, I was recognised as a human being.”
Mr Mandela’s widow, Graca Machel, arrived at the stadium to huge cheers as she was shown on the big screen.
There were cheers too of “Winnie! Winnie!” for ex-wife Winnie Madikizela-Mandela, who hugged and kissed Graca Machel.
However, there were boos for current South African President Jacob Zuma.
He will make the keynote address, and other tributes will come from Brazilian President Dilma Rousseff, Chinese Vice-President Li Yuanchao, President Hifikepunye Pohamba of Namibia and Indian President Pranab Mukherjee.
Raul Castro’s speech reflects the fact that under his brother, Fidel, Cuba was a staunch critic of apartheid, and Mr Mandela had expressed gratitude for that support.
There was a large cheer from the crowd as Raul Castro’s name was read out.
The BBC’s Mike Wooldridge in Johannesburg says the line-up of world leaders is a sign of how South Africa has seen its partners and place in the world since Nelson Mandela became president.
But, he adds, today is as personal as it is political… a recognition that there are lessons for the wider world in everything Nelson Mandela sought to achieve.
British Prime Minister David Cameron is attending Tuesday’s memorial, along with Deputy Prime Minister Nick Clegg, Labour leader Ed Miliband and former British Prime Ministers Gordon Brown, Tony Blair and John Major.
Mr Cameron told the BBC how he had been struck by Mr Mandela’s “incredible grace and forgiveness – how he reconciled people after all those years in jail”.
Three former US presidents, George W Bush, Bill Clinton and Jimmy Carter, are also attending, as are Francois Hollande of France, Palestinian leader Mahmoud Abbas and Zimbabwe’s President Robert Mugabe.
Other mourners on the list are Oprah Winfrey, Bono, Sir Richard Branson and Peter Gabriel.
They join the crowd at FNB stadium, also known as Soccer City, just outside Johannesburg, near Soweto.
Mr Mandela made his final major public appearance there during the 2010 football World Cup.
The memorial service, which had been due to start at 11:00 (09:00 GMT), will last about four hours, according to the official programme.
Because public seating is not ticketed, the South African authorities felt many people would have to be turned away and set up big screens at three “overflow” stadiums – Orlando, Dobsonville and Rand.
However, correspondents say that the heavy rain, security and transport issues and the fact that Tuesday was not declared a national holiday have kept the numbers down.
Mr Mandela’s body will lie in state in Pretoria on the following three days and a state funeral takes place on Sunday in his home village of Qunu in Eastern Cape province.
Two of Mr Mandela’s granddaughters, Tukwini and Nandi, told the BBC the family had been working to give him “the beautiful send-off that he deserves”.
More than 100 current or former heads of state or government will attend the funeral or the national memorial, according to the South African government.
Among those not attending the memorial events will be Israel’s Prime Minister Benjamin Netanyahu, who cited high travel and security costs.
However there will be suspicion that he wishes to avoid the potential for anti-Israeli protests, the BBC’s Middle East Correspondent Kevin Connolly reports. Israel had extensive links with the old apartheid regime and many South Africans identify strongly with the Palestinian cause, our correspondent adds.