CAPE TOWN - Nelson Mandela, 91, may be increasingly frail but he remains a towering icon of peace and tolerance including for his role in the defeat of apartheid and as South Africa's first black president.

The white minority government sentenced him to life imprisonment in 1964 for sabotage but, amid mounting international pressure, released him on February 11, 1990 — an historic event remembered across the world Thursday.

"I greet you all in the name of peace, democracy and freedom for all," he said in his first address, with arms outstretched on the balcony of Cape Town's city hall where 50,000 people clamoured to welcome him.

"Our struggle has reached a decisive moment," he said. "We call on our people to seize this moment so that the process towards democracy is rapid and uninterrupted. We have waited too long for our freedom."

Four years later, the prisoner became president, setting South Africa on a course toward reconciliation by restoring dignity to the black majority and reassuring whites they had nothing to fear from change.

"When he emerged from prison, people discovered that he was all the things they had hoped for and more," said his fellow Nobel prize winner, Archbishop Desmond Tutu.

"He is by far the most admired and revered statesperson in the world and one of the greatest human beings to walk this earth."

Rolihlahla Dalibhunga Mandela, affectionately known by his clan name "Madiba", was born in Mvezo village in one of South Africa's poorest regions, the former Transkei. He is the great-grandson of a Tembu king.

He was given his English name, Nelson, by a teacher.

An activist since his student days at Fort Hare University College in southeastern South Africa, Mandela opened the country's first black law firm in Johannesburg in 1952 with fellow activist Oliver Tambo.

He became commander-in-chief of the anti-apartheid African National Congress party's armed underground wing, Umkhonto weSizwe (Spear of the Nation), in 1961 and the following year underwent military training in Algeria and Ethiopia.

After more than a year underground, Mandela was captured by police and sentenced in 1964 to life in prison at the Rivonia trial, where he delivered a speech that was to become the manifesto of the anti-apartheid movement.

"During my lifetime, I have dedicated myself to this struggle of the African people. I have fought against white domination and I have fought against black domination. I have cherished the ideal of a democratic and free society.

"It is an ideal for which I am prepared to die," he said.

Mandela was jailed on Robben Island for 18 years before being transferred in 1982 to Pollsmoor prison in Cape Town and later to Victor Verster prison in nearby Paarl.

Hardline President PW Botha was replaced in 1989 by the more conciliatory FW De Klerk, who ordered Mandela's release, heralding the end of 46 years of apartheid. Both men were awarded the Nobel Peace Prize in 1993.

Mandela embodied the hopes of his nation in April 1994 when he cast his ballot for the first time in his life in South Africa's first all-race election.

In office, he used a keen sense of the power of symbolism to push reconciliation, famously having tea with the widow of apartheid architect Hendrik Verwoerd, and donning the jersey of the mainly white Springboks at their 1995 Rugby World Cup win.

Mandela served only one five-year term as president but later devoted his energy to mediating conflicts, including the war in Burundi.

In 1998, on his 80th birthday, Mandela — who divorced Winnie Madikizela-Mandela in 1996 — married Graca Machel, the widow of Mozambican president Samora Machel.

In 2005, he announced his only surviving son had died of AIDS.

Today Mandela is mostly out of the public eye, making rare appearances including at gatherings of the African National Congress, his party since 1942, and then usually on the arm of his wife or an aide.