U.S. President Barack Obama has called the widow of Nelson Mandela to express his condolences.
President Obama spoke with Graca Machel Friday to tell her of the profound influence Mr. Mandela had on his life.
He also thanked Mrs. Machel for the joy she brought to her late husband's life and the commitment to a peaceful, fair and loving world that she and President Mandela shared.
Earlier at the White House, a solemn President Obama called Mr. Mandela an influential, courageous, and profoundly good human being.
"I am one of the countless millions who drew inspiration from Nelson Mandela's life. My very first political action, the first thing I ever did that involved an issue, or a policy, or politics, was a protest against apartheid. I would study his words and his writings. The day he was released from prison gave me a sense of what human beings can do when they're guided by their hopes and not by their fears."
Mr. Obama said flags at the White House and other public buildings will fly at half staff through Monday, in a rare gesture toward a foreign leader.
F.W. de Klerk, South Africa's last apartheid leader, said Mr. Mandela's greatest legacy is his emphasis on reconciliation. De Klerk won a Nobel Peace Prize alongside Mr. Mandela, whom he freed from prison in 1990. He said their relationship was "often stormy," but that they were "always able to come together at critical moments."
Many African leaders, who were in Paris for a security summit Friday, vowed to live up to the example Mr. Mandela set.
South African Archbishop and anti-apartheid activist Desmond Tutu called his friend a "precious diamond" who emerged from prison "virtually flawless." Tutu said instead of "calling for his pound of flesh, he proclaimed the message of forgiveness and reconciliation."
Ex-U.N. chief Kofi Annan, who along with Tutu and Mr. Mandela formed a group of statesmen known as The Elders, said South Africa was fortunate to have a leader that inspired forgiveness so that the country "did not go up in flames."
Fellow Nobel Peace Prize winner Aung San Suu Kyi paid tribute to Mr. Mandela as a "great human being who raised the standard of humanity."
"He made us all understand that nobody should be penalized for the color of his skin, for the circumstances into which he is born. He also made us understand that we can change the world. We can change the world by changing attitudes, by changing perceptions."
The Dalai Lama, another Nobel Peace laureate, said he will "personally miss a dear friend" he had hoped to meet again. He said that although Mr. Mandela has physically departed, his "spirit will go on"
India's Prime Minister Manmohan Singh called Mr. Mandela "a giant among men," and compared him to India's own icon of freedom and reconciliation, Mahatma Gandhi.
Meanwhile, U.N. Secretary General Ban Ki-moon called on people to be inspired by Mr. Mandela to keep working for a better and more just world.
"Nelson Mandela showed what is possible for our world and within each one of us - if we believe, dream and work together for justice and humanity. His moral force was decisive in dismantling the system of apartheid."
Former U.S. Presidents Jimmy Carter, Bill Clinton, and George W. Bush also praised Mr. Mandela as a champion of freedom, human dignity, and equality.
Another ex-U.S. president, George H. W. Bush, called Mr. Mandela, "a man of tremendous moral courage, who changed the course of history in his country."
British Prime Minister David Cameron emerged from 10 Downing Street to call Mr. Mandela a true global hero, saying a great light has gone out in the world.
Israeli Prime Minister Benjamin Netanyahu called him a man of vision who rejected violence and was one of "the most honorable figures of our time."
Palestinian President Mahmoud Abbas, meanwhile, hailed Mr. Mandela as a "symbol of freedom from colonialism and occupation," calling his death "a great loss."
Chinese President Xi Jinping expressed "deep grief" at the death of what he called a "world-renowned statesman." He said Mr. Mandela, who visited China twice, will always be remembered for his contributions to China-South African ties "and the cause of human progress."
Haitian President Michel Martelly said Mr. Mandela remains a "symbol of democracy" whose courage and "faith in the true struggle for equality" continue to guide mankind.
Pope Francis also expressed condolences, and said he prays that Mr. Mandela's example will inspire generations of South Africans.