Argentina has begun three days of national mourning following the death of Raul Alfonsin, a former president who oversaw the country's return to democracy in the 1980s after seven years of military rule.
The 82-year-old, who died on Tuesday from lung cancer, had won international praise for putting former military rulers on trial for the torture and killing of their opponents.
Cristina Kirchner, the current president, said Alfonsin was "inextricably linked" to the restoration of democracy.
"He was a strict man who defended his beliefs and that is something very valuable," Kirchner said in London, where she is attending the G20 summit of major world economies.
A political activist from his teens, Alfonsin was jailed three times by two governments in the 1960s.
He was an influential human-rights leader during the 1970s and under military rule, risking his life by offering free legal services to those abducted by security forces.
Alfonsin was elected president in October 1983 following the collapse of the military government in the wake of their defeat by Britain in the Falklands War of April 1982.
Five military officers were convicted and imprisoned for human-rights crimes in the trials he set up. An official report estimated that 11,000 people disappeared and died under 1976-1983 period of military rule.
Alfonsin survived three military uprisings against his rule, but his term ended when his Radical Party, discredited for its handling of an economic crisis, was heavily defeated at the ballot box by Carlos Menem, a politician from the Peronist party, in 1989.