BUENOS AIRES (AFP) - A colleague who says he gave a gun to an Argentine prosecutor found fatally shot earlier this week has been barred from leaving the country, justice officials in Buenos Aires said.

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

Nisman was found dead with a a bullet to the head in his Buenos Aires home Sunday, just before he was to go before a congressional hearing to accuse President Cristina Kirchner of shielding Iranian officials implicated in a bomb attack on a Jewish community center in 1994 that left 85 dead.

Investigators, who initially said he appeared to have committed suicide, have not ruled out homicide or "induced suicide," while Kirchner has said she believes Nisman was murdered in a plot to implicate her government in a cover-up.

Prosecutor Viviana Fein, who is leading the investigation, said Saturday in a statement that investigators are "waiting for completion of ballistics analysis, including a DNA comparison and to see whether the bullet taken from the body corresponds to the .22-caliber weapon found at the scene."

Before his demise, Nisman had filed a 280-page complaint charging that Kirchner had issued an "express directive" to shield a group of Iranian suspects in the 1994 bombing.

Nisman contended that the government had agreed to swap grain for oil with Teheran in exchange for withdrawing "red notices" to Interpol seeking the arrests of the former and current Iranian officials accused in the unsolved case.