Italian justice has begun investigating ex-civil security chief Guido Bertolaso, who could face involuntary homicide charges of under-estimating the impending dangers ahead of a killer quake in 2009.

The probe, announced Tuesday, was opened after a complaint from a lawyer in L'Aquila where some 300 people died in the quake that devastated the capital of Abruzzo, east of Rome.

The lawyer in question got hold of a recording of a compromising telephone conversation purportedly between Bertolaso and a regional advisor.

In the conversation, which took place on March 30, 2009, a week before the L'Aquila quake, Bertolaso spoke of a meeting of a national committee on major risks, charged with evaluating whether an earthquake might be in the offing and the need to prepare those at risk.

Bertolaso, according to the transcript of the phone calls, calls the meeting a "media event" organised "not because we have any fears or are concerned but to reassure the people."

Magistrates in L'Aquila want to bring together a separate action launched against members of the risks committee and the claims against Bertolaso and judge them together for having under-estimated the likelihood of a major quake.

An involuntary homicide case against seven scientists on the risks panel opened last September.

The Italian scientists are accused of failing to predict the earthquake in the medieval university city in central Italy, despite signs of increased seismic activity in the area.

Prosecutors say residents around the city of L'Aquila in the mountainous Abruzzo region should have been warned to flee their homes in the days before the quake.

According to the indictment, the seven are suspected "of having provided an approximative, generic and ineffective assessment of seismic activity risks as well as incomplete, imprecise and contradictory information."

Some 120,000 people were affected by the 6.3 magnitude quake, which also destroyed the city's historic centre and medieval churches as well as surrounding villages.