BUENOS AIRES — Argentina’s government on Wednesday cast greater suspicion on an aide to Alberto Nisman, the prosecutor whose mysterious death this month has shaken the country, by describing the aide as an intelligence operative — adding to its assertions that rogue spies were involved in the events around Mr. Nisman’s death.

“This kid’s situation is starting to look worrisome,” Aníbal Fernández, the president’s chief of staff, told reporters here Wednesday morning, referring to the aide, Diego Lagomarsino, 35.

Mr. Lagomarsino worked in the prosecutor’s investigative unit as an information technology consultant and lent Mr. Nisman the .22-caliber Bersa pistol used in his death, investigators say.

Before Mr. Nisman was found dead in his apartment this month, he made the explosive assertion that President Cristina Fernández de Kirchner had tried to reach a secret deal with Iran to shield Iranian officials from responsibility in the 1994 bombing of a Jewish cultural center in Argentina, which killed 85 people.