Protesters set fire to at least two buses, forcing passengers to flee, and blocked some two dozen streets with burning barricades in the capital Santiago on a day of nationwide demonstrations.
Launched in 1981, Chile's "pension fund administrators" (AFPs) have been held up by pro-market politicians and pundits worldwide as a model of how to privatize a national pension system.
But opponents say the system has left the 10 million Chileans enrolled in it with deplorable retirement benefits far short of the Pinochet regime's promise of 70 per cent of workers' last paychecks.
The yesterday's protests came on the same day as a strike by public sector workers demanding a raise, adding to the pressure on center-left President Michelle Bachelet.
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Protesters disrupted the morning commute in Santiago by blocking off streets and attacking buses with Molotov cocktails.
Thousands later gathered at a central square in Santiago, the Plaza de Armas.
"I'm 70 years old and I worked for more than 40 years for the government. My pension is 300,000 pesos (USD 460) a month," said retiree Juan Ugarte.
"I don't know what the solution is, but no more AFPs."
Some 10,000 people protested in Santiago and 58,000 nationwide, the interior ministry said.
On August 21, another protest against the pension system drew half a million people, according to organizers. It was one of the largest marches in recent years in Chile.
Pinochet's dictatorship lasted from 1973, when he came to power in a military coup, until 1990. It remains heavy baggage for Chile.
Despite the atrocities committed by his regime, which killed an estimated 3,200 people and tortured 38,000, Chile's constitution and much of its policy framework still date to his rule.
But her popularity has since plunged amid a corruption scandal involving her son, and it is unclear whether she still has the political capital to deliver on her reform agenda.