A one-eyed former neo-fascist gangster and 45 other defendants went on trial today day accused of running a mafia crime ring in Rome that skimmed millions of euros off city hall contracts.

Prosecutors say their year-long investigation has laid bare systematic corruption within Rome as politicians, bureaucrats and businessmen hooked up with mobsters to rig public tenders on everything from creating refugees centres to rubbish collection.

Massimo Carminati, a one-time member of Rome's notorious far-right Magliana Gang, and his sidekick Salvatore Buzzi, a convicted murderer, are accused of running the crime ring, which prosecutors say represented a new type of mafia in Italy.

Neither man will appear in court during the trial, which is expected to last until at least next July, but will follow proceedings via video links from the high security jails where they are being held.

They have denied any mafia links -- a crime which carries longer prison terms and tougher jail conditions than simple corruption convictions.

"In this whole story, the thing which has really annoyed Carminati is the fact that his name has been associated with the words 'mafia' and 'drugs'. He has nothing to do with the mafia," said his lawyer Giosue Naso as he arrived at the courthouse.

Prosecutors have some 36,000 hours of wiretaps to back up their case, Italian media reported, as well as secretly filmed video showing some of the accused receiving bribes.

An initial, fastracked trial tied to the scandal ended on Tuesday, with four defendants, including a senior city official, found guilty and handed prison terms of between four and five years. The judge agreed that it represented a mafia ring.

Police say the group operated like a mafia clan, but independently of established southern mafias such as Sicily's Cosa Nostra, the 'Ndrangheta in Calabria and Camorra in Naples. In exerting such broad political control over public contracts, its focus ran beyond traditional Mafia areas of extortion, money laundering and drugs.

Prosecutors allege that mobsters flourished in Rome following the 2008 election of right-wing mayor Gianni Alemanno, who is under investigation for graft, but does not face any mafia-related charges and is not involved in this trial.

Alemanno's successor, the centre-left Ignazio Marino, is not implicated in the case, but was forced to resign last week following in an unrelated expenses scandal.