ROME -- Italy's parliament headed toward an unprecedented split today between Prime Minister Silvio Berlusconi's conservative coalition and one led by his center-left rival -- the result of a national vote that could stall the formation of a new government.
Final results in the two-day vote ending yesterday showed Romano Prodi's center-left coalition gaining control in the lower house of parliament, with 49.8 percent of the vote compared with 49.7 won by Berlusconi's conservatives. The winning coalition is automatically awarded 55 percent of the seats.
According to the results, Berlusconi's center-right coalition held a one-seat lead in the Senate; six seats elected abroad were still to be counted, but if the lead stands, the split could usher in a new period of political instability for Italy.
''Until the very end we were left in suspense, but in the end victory has arrived," a jubilant Prodi told supporters.
Berlusconi's spokesman contested the declaration of victory, and a top official in Berlusconi's Forza Italia party indicated the conservatives would request a recount ''in order to have a result that we really can consider certain and final."
The official, Sandro Bondi, also accused Prodi of having ''a politically irresponsible and adventurous attitude."
Prodi's allies conceded after his announcement that results in the Senate were still not complete.
During his tenure as prime minister, Berlusconi, a flamboyant billionaire, had strongly supported President Bush over Iraq despite fierce Italian opposition to the war. Prodi, an economist, said he would bring troops home as soon as possible, security conditions permitting. But the issue was largely deflated before the campaign began, when Berlusconi announced that Italy's troops there would be withdrawn by year's end.
For hours after the vote ended yesterday, projections and returns swung dramatically back and forth between the two, and without the vote from abroad, the election's outcome was still unclear. Voter turnout was about 84 percent.
The Senate and lower chamber of parliament have equal powers, and any coalition would have to control both in order to form a government. Some center-left and center-right leaders have said if neither side controls both houses, new elections should be called.
''If there's a different majority between the Senate and the Chamber we need to go back to the polls," Luciano Violante, a leading center-left lawmaker, said earlier in the day.
If parliament is split, President Carlo Azeglio Ciampi, a highly respected economist and independent from partisan politics, could try to name a government of technocrats at least until another election. He could also seek to fashion a coalition of left and right, but considering the bitter divisions among Italy's political parties, that does not seem probable.
There is no clear provision in the Italian constitution to deal with a split parliament, and there are no precedents.
Culture Minister Rocco Buttiglione and several other politicians said early today that both sides must pull together, if only to handle urgent economic matters and the election of a new president after Ciampi's mandate expires in May.
''We have to immediately send a message to the markets, to whomever wants to invest in Italy that the country is not going to fall apart," Buttiglione said.
Berlusconi, a 69-year-old media mogul and Italy's longest-serving prime minister since World War II, was battling to capture his third term with an often squabbling coalition of his Forza Italia Party, the former neo-fascist National Alliance, pro-Vatican forces, and the anti-immigrant Northern League.
The 66-year-old Prodi, a former premier, was making his comeback bid with a potentially unwieldy coalition of moderate Christian Democrats, Greens, liberals, former Communists, and Communists.