The Elders - a group of global leaders set up by Mr Mandela to pursue peace and human rights - said they "join millions of people around the world who were inspired by his courage and touched by his compassion".

The group's chair, Kofi Annan, said the world had lost "a clear moral compass".

"While I mourn the loss of one of Africa's most distinguished leaders, Madiba's legacy beckons us to follow his example to strive for human rights, reconciliation and justice for all."

The UN Secretary General Ban Ki-moon has paid tribute to Nelson Mandela, saying that he was a "giant for justice and a down-to-earth human inspiration".

Mr Ban said that Nelson Mandela showed "what is possible for our world".

He added: "Let us continue each day to be inspired by Nelson Mandela's lifelong example - to keep working for a better and more just world".

UN Secretary General Ban Ki-moon said he was "a giant for justice and a down-to-earth human inspiration".

"Many around the world were greatly influenced by his selfless struggle for human dignity, equality and freedom. He touched our lives in deeply personal ways."

US President Barack Obama said Mr Mandela achieved more than could be expected of any man.

"He no longer belongs to us - he belongs to the ages," he said, adding that Mr Mandela "took history in his hands and bent the arc of the moral universe towards justice".

Mr Obama, the first black president of the United States, said he was one of the millions who drew inspiration from Mr Mandela's life. He has ordered that the White House flag be flown at half-mast.

FW de Klerk, who as South Africa's last white president ordered Mr Mandela's release, called him a "unifier" and said he had "a remarkable lack of bitterness".

He told the BBC Mr Mandela's greatest legacy "is that we are basically at peace with each other notwithstanding our great diversity, that we will be taking hands once again now around his death and around our common sadness and mourning".

UK Prime Minister David Cameron said "a great light has gone out in the world".

Earlier this year, Mr Mandela spent nearly three months in hospital with a recurring lung infection.

He was moved to his home in the Houghton suburb of Johannesburg in September, where he continued to receive intensive care.