Portillo said he acted to prevent history repeating itself

The government has vowed to do all it can to prosecute those responsible and compensate victims' families.

"We are doing this today so that the dramatic history we have lived through isn't repeated," President Portillo said.

President Portillo, who took office in January, campaigned closely with former president Efrain Rios Montt, whose 1982-83 regime saw some of the worst civil rights abuses of a conflict that left 200,000 dead.

The government signed a peace accord with rebel forces in 1996.

A "truth report" sponsored by the United Nations two years later concluded that the army had been responsible for most of the abuses during the civil war.

Brave

President Portillo's admission was welcomed by the Organisation of American States.

"It is very courageous what the president did today," said Claudio Grossman, a Chilean member of the OAS' Inter-American Human Rights Commission.

The commission said it would be monitoring the government's progress.

Other cases in which the authorities have now admitted involvement include the disappearance of journalist Irma Flaker in 1980, the killing of 12 university students in 1989, and the murder of anthropologist Myrna Mack in 1990.

Police insisted that the motive for Mack's murder was robbery, even after a man was extradited from the United States, found guilty and sentenced to 25 years in jail.

Mack's research had uncovered an army campaign against refugees displaced by the civil war.