A top South African human rights lawyer George Bizos, best known for defending Nelson Mandela at his trials died Wednesday aged 92.

According to media reports, President Cyril Ramaphosa announced his death, saying Bizos had "contributed immensely to our democracy".

Ramaphosa went on to describe Bizos as an "incisive legal mind", adding that his death was "very sad for us as a country."

Bizos' family said he died peacefully at home of natural causes.

The Nelson Mandela Foundation said "another giant of South African history and of global struggles for justice has fallen."

Besides representing some of South Africa's best known political activists during the apartheid years, Bizos was one of the architects of the country's new constitution.

Widely known for his work with Mandela, Bizos met the former while studying law in Johannesburg.

Later, he was one of the lawyers who represented Mandela at his treason trial, which began in 1956.

Bizos also represented Mandela during the Rivonia Trial, when he and other anti-apartheid activists were sentenced to life imprisonment in 1964 on charges of seeking to overthrow the apartheid government.

The Nelson Mandela Foundation said Bizos played a "critical role... both professionally and as a family friend" during the years of Mandela's incarceration.

The foundation said the friendship between the men "spanned more than seven decades and was legendary."

"In the last years of Mandela's life, they were often to be found together, just catching up, sharing memories, or heading off on car rides to see, one more time, places of significance in their life journeys," it added.

Bizos was born in Greece but came to South Africa at the age of 13 as a World War II refugee.

He later trained as a lawyer at South Africa's Witwatersrand University, before being admitted to the Johannesburg Bar.

After the end of apartheid, Bizos helped to write South Africa's new constitution.

He also represented families of anti-apartheid activists who were killed during apartheid at the Truth and Reconciliation Commission.

Reports indicate that in one of his last major trials, he secured government pay-outs for families of 34 mine workers who were killed by South African police in 2012.