Jailed mafia boss's death threat: I'll cut up prosecutor like a tuna

A death threat by a Sicilian mafia boss against the lead prosecutor in a historic mob trial has stirred grim memories of the murders of Italy's top prosecutors two decades ago.

Salvatore "The Beast" Riina, the boss of all Sicilian mafia bosses at least until his arrest in 1993, was captured by hidden microphones and prison cameras threatening Palermo prosecutor Antonino Di Matteo while talking to a fellow inmate.

"I'll cut him up like a tuna," Riina said of Di Matteo last week, according to judicial sources in Palermo who have heard the secret recordings. Bosses in the Sicilian mob, or Cosa Nostra, maintain their status and power even behind bars.

Riina's threat comes 20 years after Palermo saw magistrates Giovanni Falcone and Paolo Borsellino killed by mafia bombs.

Di Matteo is the lead prosecutor in a case - being held in Milan for security reasons - in which Italian officials are accused of holding negotiations with the mob at the time of the bombings.

He did not attend the Milan hearings on Thursday and has been put under "exceptional level 1" protection, the same as that for the president and prime minister.