Protesters and police have clashed during events to mark the 32nd anniversary of Chile's military coup.
The violence is being blamed on anarchist groups
Violence erupted in a cemetery, where thousands had gathered to pay tribute to the more than 3,000 victims of Gen Augusto Pinochet's 1973-1990 regime.
Chile's centre-left government blamed the clashes on "infiltrators". A teenager is reported to have been killed in later disturbances.
Gen Pinochet stayed at home and was visited by former aides.
At least 9,000 people marched 3km (1.8 miles) to the General Cemetery in the Chilean capital, Santiago.
Many of them carried flags of the Communist party and of other left-wing movements, as well as pictures of former President Salvador Allende who committed suicide when the military took over the presidential palace on 11 September 1973.
Marchers demanded justice for the victims of the military regime and protested against recent moves to pardon some officers convicted of human rights abuses.
Some 10,000 police officers were deployed to keep order.
But after a few incidents of violence outside the cemetery, clashes broke out inside, with demonstrators throwing rocks at police.
Riot police used tear gas and water cannon to disperse the protesters.
Local reports suggest the violence was instigated by hooded protesters, believed to be members of an anarchist group.
Later in the evening, barricades were set up in a number of working class neighbourhoods in Santiago.
Some of General Pinochet's supporters rallied outside his house
A 16-year-old boy is reported to have died from a bullet wound during the protests, which continued into the early hours of Monday.
The day of violence also left 21 police officers injured. More than 80 people have been arrested.
President Ricardo Lagos - who has come under fire for pardoning an officer who killed a trade union leader in 1982 - made a call for unity.
"I think the time has come to overcome this grey and dark moment," he said, referring to the coup.
"It is not about forgetting the past, but about using those experiences so that things like that do not happen again."