ROME -- Police raided the headquarters of Silvio Berlusconi's Forza Italia party on Wednesday in what the media tycoon denounced as a leftist plot to rob him of victory in next weekend's watershed Italian elections.


The plainclothes officers arrived a few hours before Berlusconi was set to confront his main rival Achille Occhetto, leader of the ex-Communist Democratic Party of the Left, in the key television debate of a long and bitter campaign.


Police said two officers of the elite DIGOS political branch entered Forza Italia's Rome headquarters to obtain a list of the conservative movement's candidates in the March 27-28 election.


They acted at the request of deputy public prosecutor Maria Grazia Omboni, from the southern Calabrian town of Palmi, who is investigating links between freemasons, politics and crime. Her reasons were not immediately clear.


Berlusconi said in a statement: "Such things have never happened before in our democracy. These things happen only in totalitarian countries. In a free country the voters are the judges of the parties which seek their support."


He said he had requested a meeting with President Oscar Luigi Scalfaro "to end this provocation against the freedom of Italians."


The raid took place as a mud-slinging match raged between Berlusconi and his political opponents over allegations that Forza Italia was the Mafia's choice in the elections


The row reached fever pitch on Tuesday night when Berlusconi demanded the resignation of the chairman of parliament's anti-Mafia commission, leftist politician Luciano Violante.


Violante was quoted by La Stampa newspaper on Tuesday as saying that Marcello Dell'Utri, head of Berlusconi's Publitalia advertising agency and the driving force behind Forza Italia, was on a list of suspects in an investigation into drugs and arms trafficking by the Sicilian Mafia.


Violante has denied making the remarks, which magistrates say are untrue.