Convened by a group of relatives of those killed, thousands of people gathered in downtown Santiago for a march to a memorial erected at a cemetery to commemorate the 3,225 victims of the late general's bloody 1973-1990 dictatorship.

The demonstrators marched peacefully through the streets of the Chilean capital, unable to approach the presidential palace La Moneda, kept under tight police security.

It was there that the socialist government of Salvador Allende, the first and only Marxist to come to power in Chile through a popular vote, died on September 11, 1973 as military forces surrounded the palace. He is believed to have committed suicide.

The march in his memory and those of the dictatorship's victims ended, however, with incidents near the cemetery, where a group of hooded men began to confront the police guarding La Moneda.

Some demonstrators threw sticks and stones at police officers, burned tires and other objects, as well as attacked some journalists and photographers at the site.

Police responded by dousing the crowd with water cannons and firing tear gas to disperse the demonstrators. Twenty people were arrested in the clashes, police said.

In anticipation of further incidents at night, the government launched a special security operation, while most businesses closed early.

Copyright AFP (Agence France-Presse), 2011