Students, professors and state workers walked off the job at the urging of the country's largest union, ignoring a package of measures announced by Pinera aimed at quelling the violence.
"THE STRIKE IS ON! We say it loud and clear: enough of the increases and abuses," said the Workers' United Center of Chile, which organized the two-day action alongside about 20 other groups.
In the capital Santiago, police used water cannons to disperse protesters.
"Chile has awakened," read the sign of one protester -- a slogan that has been popular since the protests against social and economic woes, and a yawning gap between rich and poor, began last week.
The country, usually one of the most stable in Latin America, has experienced its worst violence in decades since protests against a now-scrapped hike in metro fares escalated dramatically on Friday.
A four-year-old child and a man were killed on Tuesday when a drunk driver rammed into a crowd of demonstrators, Interior Undersecretary Rodrigo Ubilla said.
A third person died after being beaten by police, according to the victim's family.
The armed forces announced a nighttime curfew for the fifth day running, although at just six hours, Wednesday night's is the shortest yet.
In an address to the nation late on Tuesday, Pinera apologized for failing to anticipate the outbreak of social unrest.
"I recognize this lack of vision," Pinera said after a meeting with some of Chile's opposition leaders.
Beyond the dead, another 269 people have been injured and about 1,900 have been arrested, according to the National Institute for Human Rights.
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