Challenger Romano Prodi's center-left coalition won a narrow victory in the Italian parliamentary election, official results showed Tuesday, but Conservative Prime Minister Silvio Berlusconi refused to concede defeat.

The Interior Ministry assigned Prodi's coalition — an unwieldy alliance ranging from Catholics to communists — four Senate seats chosen by Italians voting abroad, giving him the margin he needs to win both houses of Italy's parliament.

That did not persuade Berlusconi. "Nobody now can say they have won," he said.

He said the overseas vote that decided the final Senate seats was far from decided, and there were "many irregularities and it's possible that we won't be able to confirm that it has been a valid vote."

"We won't hesitate to recognize the political victory for our adversaries — but only once the necessary legal verification procedures have been completed," he said. His camp called for a recount in the lower house, the Chamber of Deputies, which Prodi's forces won with a 25,000-vote margin out of 38 million ballots cast.

The Interior Ministry said the overall results must still be confirmed by Italy's highest court, and that parliament's election committees would have to rule on any challenges.

Berlusconi suggested Italy could follow Germany's lead and create a "grand coalition" of left and right if final results show neither side in control of both houses of parliament.

"I think that we maybe need to take the example of another European country, perhaps like Germany, to see if there's not a case to unify our forces to govern in agreement," he said.

Prodi dismissed Berlusconi's suggestion for a "grand coalition" and said the prime minister's complaints were "out of line."

"We went before voters with a precise coalition," the Apcom news agency quoted Prodi as saying. "We will govern" with the coalition majority, he said.

Prodi claimed victory well before the Senate figures were in, later saying he was not concerned about the call for a recount.

A former European Commission president, Prodi said his government would put Europe at the center of its policies.

"This is a profoundly European result, and as I said, Europe will be the center of the policy of my government," he said, also promising "constructive relations with the United States."

Prodi was strongly opposed to the U.S.-led war in Iraq, while Berlusconi supported Washington and sent 3,000 troops after the ouster of Saddam Hussein.

But Italians were mainly preoccupied with finances, not Iraq, when they cast their ballots Sunday and Monday.

Berlusconi, 69, a billionaire whose business empire includes TV networks, failed to revitalize a flat economy but promised to abolish a homeowner's property tax. Prodi, 66, said he would revive an inheritance tax abolished by Berlusconi, but only for the richest; he also promised to cut payroll taxes.

On Tuesday, Prodi said he would not install a new government until parliament names a new president in early May. In Italy, the president gives the winner the mandate to form a new government. President Carlo Azeglio Ciampi's term expires next month.

Prodi said his government would be for all Italians, "even those who didn't vote for us."

"Today we turn a page," he said. "We leave behind the sourness of long and difficult electoral campaign. We need to start immediately to repair the tears that were produced in the country."

Final returns Tuesday for the Chamber of Deputies showed Prodi winning by one-tenth of a percentage point: 49.8 to 49.7 percent. Under Italian electoral law, 55 percent of seats are awarded to the overall winner, regardless of the scale of victory, giving Prodi's forces at least 340 seats in the 630-member lower house.

But Sandro Bondi, coordinator for Berlusconi's Forza Italia party, contested 43,000 of the votes cast. He did not elaborate.

"Let's wait for the final, definitive results," Bondi said.

In the Senate, the Interior Ministry assigned Prodi's coalition four of six seats chosen by Italians voting abroad. The tally gave Prodi a total of 158 seats to 156 for Berlusconi, leaving Prodi the minimum necessary to claim majority the house. The ministry assigned the seats on its Web site, even though full returns from overseas polling stations weren't completely tabulated.

For hours after polls closed Monday afternoon, projections and returns swung dramatically back and forth between the two coalitions, and without the vote from Italians living abroad, the election's outcome remained unclear. Voter turnout was about 84 percent.

"These results mean the country is divided in two. There needs to be a provisional government for a few months, then new elections," Marco Piva, a 49-year-old banker from Padua, said on his way to work. "This is the worst result that we could have had."