Lines more than one mile (two kilometers) long formed through the capital in the rain, with crowds shouting “Have strength!” to widowed President Cristina Kirchner.
Nestor Kirchner’s sudden death of a heart attack Wednesday, at the age of 60, plunged the nation into grief and uncertainty.
His wife led a cortege to the airport through streets lined by thousands of people carrying blue and white-striped national flags, with some crying, singing or throwing flowers.
Mourners filled the air with chants of “Nestor didn’t die, Nestor didn’t die! He lives in the hearts of our working people!”
South American leaders flew to Buenos Aires for the funeral and to console their Argentine counterpart, as news of Kirchner’s death reverberated through the continent.
Venezuelan President Hugo Chavez was among a crowd which received the family and the coffin on arrival in Rio Gallegos, in the Santa Cruz province.
Thousands braved the chilly Patagonia weather to see the coffin travel to the local cemetery.
The street scenes in Buenos Aires, in which mourning mixed with fiery political speeches, were reminiscent of the massive outpouring after the death of popular former first lady Eva Peron, or Evita, in 1952 and her husband and three-time president Juan Peron in 1974.
Cristina Kirchner and their two children earlier spent hours at the presidential palace receiving the condolences of supporters of her husband who as president was remembered for pulling the country out of an economic crisis.
Many wondered how the widowed president would cope, given the huge influence Nestor Kirchner played behind the scenes of her administration and his role as leader of Argentina’s ruling party.
Nestor Kirchner, who was president from 2003 to 2007 before clearing the way for his wife’s election, was widely believed to have been preparing to stand once again for the presidency in 2011.
The death has “changed the picture completely” in Argentine politics, said Uruguay’s President Jose Mujica, who said it “created a degree of relative uncertainty” that could be felt even in his own country.
Beside his role as key advisor on national politics to his wife, Kirchner was also the head of the Union of South American Nations (UNASUR) when he died, which gave him a high regional profile.
“More than a president, he was a friend who helped integrate South America and Latin America,” said Brazilian President Luiz Inacio Lula da Silva, who paused from an electoral campaign for his presumed successor to travel to Buenos Aires.