Dozens of world leaders yesterday joined South Africans in a memorial service for former President Nelson Mandela in Soweto.Prime Minister Pierre Damien Habumuremyi and the ruling Rwanda Patriotic Front (RPF) Secretary-General Francois Ngarambe led the Rwandan delegation to yesterday’s ceremony in Soweto.Speaker after speaker described the departed leader as an icon that will always be remembered for his contribution towards fighting for freedom for Africans."Mandela showed us the power of action; of taking risks on behalf of our ideals.  Perhaps Madiba was right that he inherited "a proud rebelliousness, a stubborn sense of fairness” from his father,” said US President Barack Obama.The former South African liberation hero died last Thursday, aged 95.South Africa is observing a series of commemorations until the funeral on Sunday."And we know he shared with millions of black and coloured South Africans the anger born of, "a thousand slights, a thousand indignities, a thousand unremembered moments… a desire to fight the system that imprisoned my people,” Obama said."It is hard to eulogise any man–to capture in words not just the facts and the dates that make a life, but the essential truth of a person–their private joys and sorrows; the quiet moments and unique qualities that illuminate someone’s soul.  How much harder to do so for a giant of history, who moved a nation toward justice, and in the process moved billions around the world,” Obama said.This was arguably one of the biggest gatherings of international dignitaries in generations.More than 100 current and former heads of state and government attended the event.Obama said Mandela demonstrated that action and ideas are not enough. "No matter how right, they must be chiseled into law and institutions.  He was practical, testing his beliefs against the hard surface of circumstance and history.  On core principles he was unyielding, which is why he could rebuff offers of unconditional release, reminding the apartheid regime that "prisoners cannot enter into contracts,” he said.In his key note address, Jacob Zuma, the South African president, said Madiba was a fearless freedom fighter, who refused to let the brutality of apartheid states to stand between him and his struggle."Under his leadership, the democratically elected governments focused on building a democratic society based on non-racialism and non-sexism,” said Zuma.He added: "Indeed Madiba was one of a kind… a fearless freedom fighter who refused to allow the brutality of the apartheid state to stand in way of the struggle for the liberation of his people.”The memorial, held at the FNB Stadium where Mandela was last seen in public at the final of the 2010 Fifa World Cup, was broadcast live across major world television, radio and Internet portals.Castro on concerted effortCuban President Raul Castro, charmed by the ‘Madiba Magic,’ smiled as he shook hands with Obama, the first such gesture by heads of state of the two countries since the Cold War more than 50 years ago.In his eulogy, Raul Castro, who succeeded his brother  and Mandela’s close friend Fidel Castro, said the anti-apartheid icon’s life teaches people that what threatens the existence of humanity can be stopped by effort from all countries."We shall never forget Mandela’s moving homage to our country’s struggles when he came,” he said.Mandela’s family friend Andrew Mlangeni, who was in prison with him on Robben Island, said he had no doubt Mandela  "is smiling as he looks down on his beloved countrymen coming together to celebrate his life.”"Nelson Mandela epitomised the values of sacrifice, wisdom and patience, and created hope when there was none. He forged optimism and confidence out of distrust and sorrow. It is impossible to compare a leader of his stature,” he said. UN Secretary-General Ban Ki-moon said there was "sorrow for a mighty loss and celebration of a mighty life.”"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,” Ban said.KigaliPreparations are underway to commemorate the legacy of Mandela in Kigali, George Nkosinati Twala, the South African envoy to Rwanda, said yesterday.Amb. Twala said they were organising the commemoration event in collaboration with Rwanda’s Ministry of foreign affairs.He said a team from South African is in the country to help organise the event."We are hoping to have a joint commemoration service and are still waiting for the final decision on exact dates, probably tomorrow (today) or next days,” he said.He said the organising team was in touch with foreign affairs ministry on how the event will be organised."Mandela is part of Rwandan community, he doesn’t belong to us alone, we all own him. He spearheaded reconciliation in this country to ensure that Rwandan pride is known worldwide,” he added.President Kagame on Monday directed that flags fly at half-mast until Sunday, the day the global icon will be laid to rest.Kagame, in his condolence message to the family of Mandela, said the late anti-apartheid hero represented "much of what is remarkable about the human spirit.”At the South African High Commission yesterday, diplomats representing their countries in Kigali and government officials continued to throng the Commission to sign in the condolence book.The signing, being done between 9am and 3pm, started on Friday, last week, and it will end on Sunday.Several top government officials who signed in the book praised Mandela’s contribution towards the development of African continent as well as his struggle for African independence."We Africans are celebrating your departure because you didn’t leave as a normal person but an exceptional one on our continent. Though you have gone, your legacy will remain forever because of what you fought for in your motherland and Africa, in general,” Venantia Tugireyezu, the Minister in the President’s office, wrote.State minister for Primary and Secondary Education Mathias Harebamungu wrote: "Our beloved Tata Madiba, we Africans have lost our shining icon. RIP but future generations should be inspired by your wisdom, patriotism, pan-Africanism.”