Judges began checking tens of thousands of contested ballots Thursday, as Italian politics was thrown into turmoil after Premier Silvio Berlusconi's demand for a recount of rival Romano Prodi's narrow parliamentary election victory.

Official returns gave Prodi's center-left coalition the majority in both houses of parliament in the April 9-10 elections — but the margin was a mere 25,000 votes in lower Chamber of Deputies.

One Italian newspaper even compared the scenario to the disputed balloting in Florida during the U.S. presidential race in 2000.

Prodi insisted Thursday that his victory is safe.

"There is nothing to worry about; we are serene," he said in Bologna, according to Italy's ANSA and Apcom news agencies.

Berlusconi has refused to concede, saying late Wednesday that the margin of victory was slim enough to require "a scrupulous check to ascertain any possible error or irregularity."

Judges were examining 43,000 ballots that were not immediately included in the overall official count because they had possible problems— but not enough to invalidate them outright.

Newspapers and politicians say checks so far indicated that they would not change the balance.

Experts say that statistically and historically it is very unlikely that any given side would be able to win 50 percent of contested ballots.

"I don't think they will change the outcome of elections," said Berlusconi ally Lorenzo Cesa, referring to the contested ballots.

A member of Prodi's coalition, Greens Leader Alfonso Pecoraro Scanio, claimed that so far more of the contested ballots were assigned to his center-left coalition than to Berlusconi's conservatives.

But Berlusconi has also demanded checks "one by one" of at least 60,000 polling stations — almost all of them — and more than 1 million annulled ballots.

"I'm confident. The results must change," the combative conservative said after meeting Wednesday night with the president. "You thought you were rid of me?"

His comments raised the heat in a country already weary from a long, bitter election campaign, and divided almost evenly between the center-left and center-right coalitions.

Italy's leading daily, the Corriere della Sera, said Berlusconi's challenge leaves Italy "even more divided than during the electoral campaign."

The paper, in an editorial Thursday, compared the political uncertainty to the 2000 U.S. presidential election, which hinged on disputed ballots in the key state of Florida.

"At this point, it is difficult not to fear a kind of 'Italian-style Florida,"' Corriere said.

The dispute could usher in an extended period of uncertainty over the results, a process which could take weeks. The outcome of the election must be approved by Italy's highest court, and it is up the president to give the head of the winning coalition a mandate to form a government

However, the president's term ends in mid-May, and the current president, Carlo Azeglio Ciampi, has said he would leave the decision up to his successor.

Parliament, which convenes April 28, has until May 13 to elect a new president, meaning a new government would not be formed until mid-May at the earliest.