The row over a corruption probe against Nicolas Sarkozy escalated Thursday, March 28 after as the judge who charged France's former president received a bullet and a death threat in the post, according to AFP.

The letter was sent to Jean-Michel Gentil, the most prominent of three judges investigating the case, on Wednesday, the magistrate's union SM revealed in a statement published on its website.The threatening letter was accompanied by blank cartridges.

One of Gentil's colleagues said the letter, mailed to his Bordeaux office, also contained threats against other magistrates. Police had been called in to investigate, the colleague added.

The SM, in its online statement, denounced what it called "insulting statements" made by Sarkozy's inner circle which it said were designed to undermine the work of the judiciary.

It noted too that Sarkozy's own lawyer, Thierry Herzog, had questioned Gentil's impartiality in an interview with Sunday newspaper Journal du Dimanche.

The SM said a number of its members were targeted in the letter. Gentil himself is not a member of the union, one colleague told AFP.

Sarkozy's lawyers are attempting to overturn last week's decision by three examining magistrates to charge him in a case that threatens to destroy his hopes of a political comeback.

Gentil last June put his name to an opinion column signed by dozens of legal professionals in Le Monde newspaper accusing Sarkozy and his predecessor Jacques Chirac of "wishing to protect the corrupt", Herzog pointed out.

Herzog added that five days after signing the column, Gentil had ordered police to search Sarkozy's home, office and his secretary's house.

The decision to place Sarkozy under formal investigation has provoked a furious reaction from his political allies.

Sarkozy himself has repeatedly denied claims he accepted cash-stuffed envelopes from the world's richest woman Liliane Bettencourt to fund his successful 2007 campaign. Medical experts say the mental faculties of the L'Oreal heiress began to deteriorate in 2006.

On Monday, Sarkozy used his Facebook page to insist he had not taken advantage of Bettencourt. Describing the charges against him as "unfair and unfounded", he vowed to clear his name.