An Argentinian prosecutor, who was found dead days after he accused former President Cristina Fernandez of covering up Iran's alleged role in the 1994 bombing of a Buenos Aires Jewish Center, was murdered, a federal judge said Tuesday.

Judge Julian Ercolini said that there was sufficient proof to show that the shot to the head that killed Alberto Nisman in his apartment in January 2015 was not self-inflicted.

"Nisman's death could not have been a suicide," Ercolini said in a 656-page ruling.

Fernandez, who was president in 2007-2015 and is currently a senator, had suggested the case was a suicide and "conspiracy” to bring down her government.

Ercolini also charged Diego Lagomarsino, a former aide of Nisman's, with accessory to murder.

Lagomarsino had admitted to lending the gun to Nisman that was ultimately used in his death, but said it was provided for the prosecutor's safety and that of his family.

Diego Lagomarsino had admitted providing the gun to Nisman, but only for his protection.

Nisman's death just a day before he was to appear before Congress to present his findings implicating Fernandez and some of her top aides in a cover-up has long sparked speculation.

What is Fernandez accused of?

A federal judge earlier this month charged Fernandez, her former foreign minister Hector Timerman and several top aides with treason and ordered their arrest in relation to an alleged cover-up around the Jewish center bombing.

The judge also requested parliament move to lift Fernandez's immunity.

Previous court decisions have cleared Fernandez of any cover up.

Nobody has ever been convicted in the 1994 bombing of AMIA Jewish center, which killed 85 people.

Iranian officials and the Lebanese Shiite group Hezbollah are believed to be behind the bombing.

The charges against Fernandez relate to a 2012 memorandum with Iran that was allegedly designed to clear top Iranian officials of involvement.

The memorandum would have allowed Iran to conduct its own investigation.

Fernandez had argued it was the only solution since Argentina had no extradition treaty with Iran and Argentinian law doesn't allow trials in absentia.

Fernandez says accusations against her are part of a witch hunt against the opposition.

However, the memorandum never went into full effect because it was not approved by Iran's parliament.

Rights groups, Interpol defend Fernandez

Former Interpol chief Ronald Noble has said that Fernandez never requested international arrest warrants for Iranian suspects be dropped.

Human Rights Watch has said that there is no evidence to substantiate treason charges against Fernandez.

The judge alleges Fernandez sought to cover up Iran's involvement in the bombing in order to normalize relations and secure a 2013 grain-for-oil deal with Tehran.

Fernandez has multiple corruption charges swirling around her. She says they are part of a witch hunt by President Mauricio Macri against opponents.

cw/jil (AFP, AP, dpa, epd, Reuters)