The attack, in which party-goers including an 8-year-old boy mistaken for leftist rebels were shot by masked gunmen, is one of the most notorious cases of alleged human rights abuses under Fujimori's 1990-2000 tenure. The killings were allegedly carried out by the Colina death squad run by Vladimiro Montesinos, who was then Peru's spy shief.
Attorney General Nelly Calderon filed a "constitutional denunciation" against Fujimori late Wednesday accusing him of being a "co-author" of the killings in the Barrious Altos district of Lima.
"This is very serious," said Daniel Estrada, chairman of a congressional sub-commission investigating the former president over allegations of murder, forced disappearances and terrorism.
"They are charges of violation of human rights. We have presented evidence based on testimonies. We have studied everything carefully so that Congress can rule," said Calderon.
She gave no details of her evidence but Estrada has cited a witness who says Fujimori knew about the death squad.
Human rights groups say the squad was formed by Montesinos to combat rising attacks by the Shining Path guerrillas. The killings were carried out with submachine guns fitted with silencers. The victims were suspected of have ties to leftist guerrillas.
Fujimori allegedly went to the National Intelligence Service headquarters "to celebrate" with the perpetrators on the day of the massacre, the newspaper El Comercio reported Thursday.
Calderon also alleged that Fujimori protected squad members from prosecution, pushing through a 1995 amnesty law that secured their release from prison for another massacre - the 1992 assassinations of nine student and a professor at La Cantuta University.
As a former president, Fujimori has immunity from prosecution.
Estrada's sub-commission expects to wrap up its investigations in 10 to 15 days and pass its findings on to the legislature for a vote to lift Fujimori's immunity. If the vote succeeds, Calderon could then bring charges against Fujimori to court.
The ex-president, in self-exile in Japan, was fired as "morally unfit" to rule last November in a corruption crisis sparked by Montesinos. Montesinos fled the country in October and remains a fugitive.
Fujimori has proclaimed his innocence. But has said he will not return to Peru, where he believes he would not receive a fair trial. He is protected from extradition in Tokyo by dual Japanese and Peruvian citizenship and the two countries do not have an extradition treaty. However, Estrada said charges of crimes against humanity could be pursued by Japanese judges.
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