Thousands of Chileans have marched in the capital Santiago to remember the more than 3,000 people killed during the dictatorship of Augusto Pinochet that was launched 38 years ago with a military coup on September 11, 1973.

Organised by a group of relatives of those killed, the march on Sunday led to a memorial erected at a cemetery to commemorate the victims of Pinochet's 17-year long regime.

They marched peacefully through the streets, unable to approach the presidential palace La Moneda because of the tight police cordon.

Salvador Allende, the first and only Marxist to come to power in Chile through a popular vote, died at the palace when military forces surrounded it during the coup.  He is believed to have committed suicide.

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

Some demonstrators threw sticks and stones at police officers, burned tyres 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.

Minor skirmishes were also reported in the neighboring port city of Valparaiso.