Nearly 100 leaders and royals from all corners of the world are descending on Johannesburg for the memorial of former South African president and anti-apartheid icon Nelson Mandela, in what has been dubbed as an unprecedented gathering of international dignitaries.

Tens of thousands of South Africans are also expected to take part in the memorial at the First National Bank (FNB) stadium, where the Noble Peace Prize laureate made his last public appearance in 2010.

The list of dignitaries who will be addressing the gathering includes US President Barack Obama, UN General Secretary Ban Ki-moon, Brazilian President Dilma Rousseff, Indian President Pranab Mukherjee, President Raul Castro of Cuba and Chinese Vice President Li Yuanchao.

Obama is being joined by First Lady Michele Obama and three former American presidents - Jimmy Carter, Bill Clinton and George Bush.

The British delegation led by Prime Minister David Cameron includes former prime ministers Gordon Brown, Tony Blair, Sir John Major, Deputy Prime Minister Nick Clegg and the Leader of the Opposition Ed Miliband.

Scores of leaders from the African continent will also be attending the ceremony.

"Kings, queens, princes and princesses will be joined at FNB Stadium by representatives of international organisations such as the United Nations, African Union, European Union, the Commonwealth and the World Bank, and other VIPs," said South African Minister Colins Chabane, who has been tasked with the arrangements.

The four-hour-long memorial ceremony will begin at 11:00 local time (09:00 GMT).

The stadium has a capacity of 95,000 people and South Africans have already started arriving as the seats are filled on first-come, first-serve basis. Rainfall is predicted throughout the day and thousands are expected to brave the rains in the open-air stadium.

Schedule of events in chronological order:

Choir sings South Africa's national anthem

Opening remarks and interfaith prayers

Speech by Mandela family friend Andrew Mlangeni

Speech by family member Gen Thanduxolo Mandela

Tribute by Mandela's grandchildren Mbuso Mandela, Andile Mandela, Zozuko Dlamini and Phumla Mandela

Speech by UN Secretary-General Ban Ki-moon

Speech by African Union Commission Chairwoman Nkosazana Dlamini Zuma

Speech by US President Barack Obama

Speech by Brazilian President Dilma Rousseff

Speech by Chinese Vice President Li Yuanchao

Speech by Namibian President Hifikepunye Pohamba

Speech by Indian President Pranab Mukherjee

Speech by Cuban President Raul Castro

Keynote address by South African President Jacob Zuma

Sermon by Bishop Ivan Abrahams