Italian ex-premier Silvio Berlusconi's warning that his centre-right party could withdraw its support for the government was seen by the press Sunday as a declaration of war against Prime Minister Mario Monti.

"In the next few days we will decide with the leadership of my party whether it is better to immediately withdraw our confidence or to keep it, given the upcoming election (in April)," Berlusconi said at a press conference on Saturday after he was sentenced to jail for tax fraud.

"We need to weigh this government policy that leads to a spiral of recession for our economy" against the way "a vote of no-confidence could be seen by the world of finance," the 76-year-old added.

Reactions to Berlusconi's comments were splashed across the front pages of the Italian press on Sunday, with the leading Corriere della Sera saying, "Berlusconi threatens to topple Monti", while other headlines declared "Berlusconi attacks Monti" and "Berlusconi against Monti".

"Berlusconi in his bunker has declared war on Monti and Merkel," leftwing daily Il Fatto Quotidiano said, referring to Berlusconi's accusation that the Italian prime minister was following policy dictated by German Chancellor Angela Merkel.

Berlusconi, who was sentenced to jail for tax fraud on Friday, last week announced he would not run in next year's election but vowed to remain in politics to reform the justice system that found him guilty.

The scandal-hit three-time premier was toppled in November last year over his handling of the economy in the face of deep financial crisis and was succeeded by Monti, a sober economist and former European commissioner.

No Monti Day

Berlusconi's latest comments came as tens of thousands of demonstrators marched in Rome during a "No Monti Day" Saturday called by unions, left-wing parties and other groups to protest at austerity measures in recession-hit Italy.

Banners carried slogans such as "Cuts, only cuts" and "Monti Out" to denounce a series of structural reforms the government has imposed in an effort to battle off the eurozone debt crisis.

Critics have accused Monti of failing to boost growth and of stifling the population with high taxes. Italy's unemployment rate is at 10.7%, but much higher among younger voters.

Sicilians were also voting on Sunday in a regional ballot on the Mediterranean island seen as a test of the political waters ahead of the national election.

Latest opinion polls say a member of Berlusconi's People of Freedom (PFL) party is running head-to-head for Sicily regional president against a candidate from the leftwing Democratic Party (PD). – Sapa-AFP.