Claudio Bonadio, the federal judge who led a series of corruption investigations against former Argentine president Cristina Kirchner, died on Tuesday at the age of 64, sources close to him said.

Bonadio, who rose to fame as the first judge to hear cases in which Kirchner was accused of graft, died at his home in Buenos Aires.

He had undergone brain surgery last year and had recently requested his leave on health grounds be extended to March 1.

"He worked a lot these last few years, we worked together for 20 years," Bonadio's secretary -- who was named only as Monica -- told TN television channel through sobs.

The judge clashed repeatedly with Kirchner, who accused him of "political persecution" in favor of her successor as president, Mauricio Macri.

Several times, Bonadio ordered Kirchner, who was president from 2007-15, be held in pre-trial detention, although she was spared jail by her parliamentary immunity.

Bonadio was the first judge to preside over a case brought by late public prosecutor Alberto Nissman, who accused Kirchner of covering up Iranian involvement in the 1994 bombing of a Jewish center in Buenos Aires that left 85 dead.

Nissman, whose fate was brought to the wider world by a Netflix docuseries, died in 2015 from a gunshot wound to the head at his home in Buenos Aires.

His death, which came just days he accused Kirchner of colluding with Iran to allow the alleged authors of the bombing to go free, remains unsolved.

Argentina's leader Alberto Fernandez, who picked Kirchner as his vice president, says he doubts Nissman died by suicide, despite acknowledging "there isn't a shred of proof" that he was murdered.

Another of Bonadio's most famous cases against Kirchner was the so-called corruption notebooks scandal.

It revolves around meticulous records kept by a government chauffeur, Oscar Centeno, of cash bribes -- allegedly worth $160 million between 2005 and 2015 -- he is said to have delivered from businessmen to government officials.

Kirchner used to call Bonadio the "gunslinger judge" in reference to a 2001 street robbery in which he shot dead two thieves.