Authorities said Diego Lagomarsino, a computer expert and colleague who said he had brought prosecutor Alberto Nisman a handgun Saturday night at his request, has been barred from leaving Argentina.

Nisman was found dead with a bullet to the head in his Buenos Aires home on Sunday, just before he was set to go before a congressional hearing to accuse Kirchner and Foreign Minister Hector Timerman of shielding Iranian officials implicated in the 1994 bombing of a Jewish community center that killed 85 people.

It was Argentina's worst terror attack in modern history. It has never gone to trial fully. Several pretrials were cancelled amid serious irregularities involving judges and Argentine intelligence staff.

Investigators, who initially said Nisman appeared to have committed suicide, have not ruled out homicide or "induced suicide."

Kirchner, meanwhile, has said she believes the 51-year-old was murdered in a plot to implicate her government in a coverup.

Prosecutor Viviana Fein, who is leading the investigation, said investigators were waiting for ballistics analysis, including a DNA comparison, and to see whether the bullet taken from the body matches the .22-caliber weapon found at the scene