Mandela memorial: Thousands gather in Johannesburg 10 December 2013 Last updated at 08:14 The atmosphere is building in the FNB stadium ahead of the service Thousands of people are gathering at a stadium in Johannesburg for a memorial service for Nelson Mandela. US President Barack Obama, Cuban President Raul Castro and UN Secretary General Ban Ki-moon will address the service, as will four of Mr Mandela's grandchildren. It will be held at the 95,000 capacity FNB stadium and be shown on big screens at three "overflow" stadiums. The former South African president died aged 95 last Thursday. The country is observing a series of commemorations leading up to the funeral on Sunday. World leaders attending US President Barack Obama UN Secretary General Ban Ki-moon Cuban President Raul Castro French President Francois Hollande British Prime Minister David Cameron Brazilian President Dilma Rousseff Zimbabwean President Robert Mugabe A mighty life The memorial service is one of the biggest gatherings of international dignitaries in recent years. 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 is beginning to have the feel of a political rally. 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. South African President Jacob Zuma 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. 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. This is Nelson Mandela's "rainbow nation" in action, thousands of black, white, Asian and coloured (mixed-race) people from all over South Africa gathered to say their goodbyes to the world icon. It has been almost 20 years since the advent of democracy but race remains a thorny issue here. Not today though - all differences are forgotten, today these people stand united for Mr Mandela. He is, after all, the reason such a diverse group of people can now gather under one roof, as equals. Struggle songs ring out throughout the stadium. Tata wethu - our father - they sing. Many stood in the rain waiting for several hours to get into the stadium. South Africans have a great ability to unite behind a great cause - as was seen during the 2010 World Cup and now at one of the biggest moments in the country's history - the death of the father of the nation. Four of Mr Mandela's grandchildren will also make speeches, along with Andrew Mlangeni, Mr Mandela's friend and fellow former Robben Island prisoner. Ban Ki-moon, who will also deliver a tribute, visited the Nelson Mandela Centre of Memory in Johannesburg on Monday. "The world mourns the loss of Nelson Mandela, one of the towering figures of our time and indeed of any time," he said. We join together in sorrow for a mighty loss and in celebration of a mighty life. 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 are expected to include Oprah Winfrey, Bono, Sir Richard Branson and Peter Gabriel. They will join a 95,000-strong crowd at FNB stadium, also know as Soccer City, just outside Johannesburg, near Soweto. Mr Mandela made his final major public appearance there during the 2010 football World Cup. Beautiful send-off The memorial service is due to start at 11:00 (09:00 GMT) and is expected to last four hours, according to the official programme. Because public seating is not ticketed, the South African authorities are certain many people will have to be turned away. So the service will be shown on big screens at three "overflow" stadiums - Orlando, Dobsonville and Rand - as well as at community venues around the country. 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. Israeli President Shimon Peres is not attending due to illness, so Knesset speaker Yuli Edelstein will represent the country. The Dalai Lama will also be among the notable absentees, after twice failing to get a visa to South Africa.