Mafia Toto Riina
Mafia boss, Toto Riina was arrested in 1993 (Reuters)

Jailed Mafia boss of bosses Salvatore "Toto" Riina has threatened to kill prosecuting magistrates over an alleged truce deal between the Italian state and Cosa Nostra in the 90s.

In an outburst of rage over the proceedings, the boss known as "The Beast" for his brutality reportedly told a fellow prison inmate that Palermo prosecutor Nino Di Matteo and his colleagues would be eliminated.

"Di Matteo shall die and all the prosecutors of the negotiation [trial] with him," Riina said in comments that were overheard by a prison guard, La Repubblica newspaper reported.

"They're driving me crazy. They have to die, even if it's the last thing I do," Riina, who is a few days short of his 83rh birthday, said.

An emergency meeting of the committee for order and security decided to step-up Di Matteo's police escort.

Riina made the comments earlier this month, after a hearing of the so called 'State-Mafia negotiation trial, which started in Palermo in May.

A team of prosecutors led by Di Matteo and including also Vittorio Teresi, Francesco Del Bene and Roberto Tartaglia, alleges that exponents of the Italian authorities secretly struck a deal with Riina to end his clan's murderous spree in the early 90s'.

Sicily was torn by a series of Mafia killing and bombings in 1992 - 1993.

The violence began with the murder of Sicilian politician Salvatore "Salvo" Lima, who was shot dead in Palermo in March 1992, and peaked a few months later with the killings of anti-Mafia prosecutors Giovanni Falcone and Paolo Borsellino, who were blown up in two separate bombings.

Palermo Prosecutors allege authorities reached out to Riina, who agreed to end the bloodshed in return for more lenient prison conditions for Mafia convicts.

Mobsters were particularly angered at the freshly introduced article 41-bis law, which imposed a hard prison regime for mafia members in an attempt to tackle bosses' ability to run their clans while behind bars.

Also known as "U Curtu" - Sicilian for "Shorty" - Riina was arrested in 1993 and is serving a life sentence in Milan's Opera prison.

The boss is standing trial in Palermo together with his jailed right-hand man Bernardo Provenzano and other mafia members, as well as several high-ranked security officials and politicians, including former interior minister Nicola Mancino and Carabinieri police corps General Mario Mori.

The accused face a wide range of charges including aggression against the state, perjury, and aiding and abetting Cosa Nostra.

The case sparked great controversy, causing tensions among different powers of the state and embarrassment to highly decorated officials.

Prosecutors have demanded some of Italy's most prominent political figures to give evidence.

Among the witnesses expected take the stand are Italian President Giorgio Napolitano and the President of the Senate Pietro Grasso.

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Italy