Left-wing and protest parties made strong gains in local elections on Monday and the center-right party of former Prime Minister Silvio Berlusconi saw heavy losses as Italian voters joined other Europeans in venting anger over austerity policies.
The results, following the victory of French Socialist Francois Hollande and major losses for traditional big parties in Greece on Sunday, will add to pressure for European leaders to ease measures adopted to counter the financial crisis.
While the vote was not directly about Prime Minister Mario Monti's government, for the two main parties that support his technocrat government in parliament, the center-right People of Freedom (PDL) and the center-left Democratic Party (PD), the vote was the biggest barometer of popular support for them ahead of national elections next year.
The 5 Star Movement led by Beppe Grillo, a shaggy-haired comedian who wants Italy to quit the euro and whose caustic invective against the established parties has gained increasing resonance in the wake of a spate of corruption scandals, made some spectacular advances.
In the northern city of Parma, it knocked Berlusconi's PDL which had previously ruled the city, into fifth place, winning a score of nearly 20 percent, while in Genoa, Grillo's hometown, it won 15 percent, knocking the PDL to fifth place, according to partial results.
At its first political test in 2010 the movement, which organises itself through the internet and social networks, won just 1.8 percent of the vote, rising to 3.4 percent at Milan's mayoral election the following year.
"Grillo has confirmed his political existence. He's the big winner," said Maurizio Pessato, vice president of polling company SWG. "The weakness of the PDL was confirmed, and perhaps it's the biggest loser of this vote."
PDL Secretary Angelino Alfano said: "There has been a defeat but this is not a catastrophe for the PDL."
More than 9 million people or some 20 percent of the electorate were eligible to vote in more than 900 towns and cities across Italy in the first significant election since Monti took office in November.
Painful tax hikes, pension cuts and unpopular labour reforms have fuelled mounting opposition to Monti since he came to power last year with a mandate to save Italy from a Greek-style debt emergency. He has placed increasing emphasis on reforms to promote growth in his recent public comments.
The election of mayors and city councillors will have no direct impact on his ability to press on with the structural reforms he has promised to revive Italy's sickly economy and control its enormous public debt.
But with national elections due in 2013 and a fragmented political landscape in which all of the main parties are in some form of trouble, Monti's ability to push ahead with unpopular reforms could be limited if the elections lead to waning support for his government.
The PDL, still struggling to re-establish its identity after the fall of its scandal-prone founder Berlusconi last year, is in particular trouble and could be tempted to rebel against unpopular measures such as a much-hated property tax.
"We support the Monti government but naturally we won't bind ourselves to vote for measures we don't agree with, that's absolutely logical," Berlusconi wrote on his Facebook page after the results.
The PD said the vote was "a real political revolution" because the center-left was in pole position in almost all the large towns that voted.
"This is a real tsunami for the center right," said Pier Luigi Bersani, the center-left leader.
However, across the country, there were also big gains for opposition or protest candidates, while abstention levels were also up in a sign of growing disaffection with the political process and all the main parties.
In Verona, Flavio Tosi, the popular Northern League mayor of the city shrugged off a corruption scandal which has rocked his party, the biggest opposition group in parliament, to return to office without the need for a runoff ballot.
In Palermo, veteran anti-Mafia campaigner Leoluca Orlando, of the opposition Italy of Values party and backed by the hard-left Refounded Communist party, had a strong lead after the first round.
Palermo's voters had "rejected the disastrous social policies of Monti's government", Orlando said.
In Genoa, Marco Doria, supported by a leftist coalition including both the PD and Refounded Communism, was comfortably ahead.
In cities where the vote was not decided in the first round, there will be a runoff ballot on May 20-21.
The turnout fell to 67 percent from 74 percent from the previous round of local elections, the Interior Ministry said.
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