Two students were shot dead Thursday in the Chilean port city of Valparaiso when protests against President Michelle Bachelet's education reform efforts turned violent, police said.
Witnesses said the victims, aged 18 and 24, were shot by a 22-year-old man who opened fire as protesters tried to graffiti his house and plaster it with posters.
The man has been detained.
The march was part of nationwide protests that swept the country's main cities as students demanded greater participation in overhauling a largely privatized and highly unequal education system inherited from late dictator Augusto Pinochet.
Violence also erupted in Santiago, where police fired water cannon to disperse masked demonstrators who attacked them with sticks and stones at the end of a march down the Alameda, one of the capital's main avenues.
Organizers said 150,000 people had joined that protest, while police put the number at 50,000.
Clashes also broke out in the southern city of Concepcion.
Students have been protesting for years, demanding reforms to the education system put in place during the 1973-1990 dictatorship.
Bachelet, Chile's first woman president, won reelection last year with promises to undertake ambitious reforms, including free university education for the poorest 70 percent of the population from 2016.
But students complain they have been sidelined from the process.
"They don't listen to us on the reforms. We want to be heard. We're disillusioned. It's the same every time, the reforms get gridlocked before they accomplish anything truly good," said Maria Jose, a 17-year-old student at the Santiago protest.
Bachelet's reform agenda has meanwhile lost momentum as her government has been embroiled in a series of corruption scandals, including one involving her son.
The leftist leader's popularity has tumbled to an all-time low of 29 percent since accusations emerged that her son, Sebastian Davalos, and his wife used political influence and inside information to make $5 million on a shady real estate deal.
Seeking to get a grip on the crisis, Bachelet named a new cabinet Monday after sacking several key ministers, including interior minister Rodrigo Penailillo, a close ally who had done consulting work for a company involved in a separate campaign finance scandal.