SANTIAGO (Reuters) - A Chilean judge formally accused six people on Friday of assassinating a former president during the country’s 1973 to 1990 dictatorship, marking the second time in a decade he has moved to resolve the enduring murder case.

Judge Alejandro Madrid charged doctor Patricio Silva, chauffeur Luis Becerra, and intelligence agent Raul Lillo of poisoning Eduardo Frei Montalva in a Santiago clinic in 1982, an act apparently instigated by the right-wing dictatorship of Augusto Pinochet, court documents showed.

Pedro Valdivia, another doctor, was accused of accessory to murder, while physicians Helmar Rosenberg and Sergio Gonzalez were accused of covering up the crime.

A lawyer for one of the accused did not immediately return messages requesting comment. Lawyers for the others could not be reached for comment.

Judge Madrid originally brought charges against the six in 2009 but they were later dismissed.

Last year, Madrid ordered the exhumation of Frei’s body and asked a number of forensic experts to examine the remains. According to the judge, the results confirmed that the former president was poisoned and strengthened the case against the accused.

While Frei initially supported the coup that overthrew socialist Salvador Allende and brought Pinochet to power in 1973, he later soured on the military dictatorship and became one of the leaders of Chile’s pro-democracy movement.

“Today, we’ve learned of the judge’s decision, and we’re very moved,” said Carmen Frei, daughter of Eduardo Frei, who governed Chile from 1964 to 1970. “All of this because my father had a conscience, because he acted firmly before the military dictatorship, because he had come to be a threat as he wanted to return to democracy.”

Pinochet died in 2006 without ever facing a full trial for human rights abuses committed under his rule, when more than 3,000 people were killed or disappeared and around 28,000 people were tortured.

In recent years, prosecutions against dictatorship-era crimes have picked up pace, as support for Pinochet - once strong among conservative sectors of society - has faded.