Police on Thursday used tear gas and water cannons to disperse hundreds of rock-throwing high school students who repeatedly blocked traffic on Santiago's main avenue. Officials said 264 people were detained.
Most shops were closing by midafternoon and many offices authorized their employees to leave earlier, as public transportation begun to disappear because of a strike by some drivers, while others feared their buses would be attacked by demonstrators.
The demonstrations came on a date often marked by violence by far-left groups commemorating what they call "The Day of the Young Combatant," honoring two young brothers killed by police in a 1985 protest of the 1973-90 dictatorship of Gen. Augusto Pinochet.
On Thursday, the judge investigating the killing of Eduardo and Rafael Vergara filed homicide charges against one active and three retired police officers. A lawyer for the retired officers, Mauricio Unda, said that they acted in self-defense during the protest.
The students' motives for demonstrating Thursday were not clear. One protester, who identified himself only as "Simon," his face covered by a white handkerchief, said only that they were demonstrating "for the situation and for our rights."
The protests were far smaller than the well-organized marches of May 2006, when up to 700,000 high-school students took to the streets to demand improved schools, lower public transportation fares and educational reforms.
The government announced Wednesday that it was mobilizing 4,000 police to prevent the violence that often breaks out on "The Day of the Young Combatant."