Center-left challenger Romano Prodi claimed victory Tuesday over Premier Silvio Berlusconi in Italy's parliamentary elections, and said he would form a "strong" government even though the official vote count was not completed. Prodi told a news conference that his government would be strong "politically and technically," rebutting concerns about an apparent slim margin of victory. The parliament appeared headed toward an unprecedented split between the conservative coalition headed by Premier Silvio Berlusconi and one led by his center-left challenger - an election result that could stall the formation of a new government and lead to a new period of political instability. Final results in the two-day vote ending Monday showed Romano Prodi's center-left coalition winning control in the Chamber of Deputies, the lower house of parliament, with 49.8 percent of the vote compared to 49.7% for Berlusconi's conservatives. The winning coalition is automatically awarded 55% of the seats, or 340 seats, according to a new electoral law. According to the results, Berlusconi's conservative allies held a one-seat lead in the Senate, although the results for six seats elected by Italians abroad were still to be counted. "We have won, and now we have to start working to implement our program and unify the country," said a jubilant Prodi, speaking to his supporters. "I am grateful to all of you because it has been a very difficult battle," Prodi said. "Until the very end we were left in suspense, but in the end victory has arrived." Berlusconi's spokesman Paolo Bonaiuti contested the victory claim, and a top official in Berlusconi's Forza Italia party suggested a recount of the vote. "At this point we think it's necessary and appropriate to demand a check and verification of the vote in the Chamber of Deputies, in order to have a result that we really can consider certain and final," Sandro Bondi told reporters. He 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. But center-left leader Francesco Rutelli was quoted as saying that the center-left was heading toward victory in the Senate as well. "In the Senate we have a one-senator lead," Rutelli, who unsuccesfully challenged Berlusconi in the 2001 elections, was quoted as saying by the ANSA and Apcom news agencies. Another leader, former center-left premier Massimo D'Alema, suggested his coalition might take four of the six seats still up for grabs, according to ANSA. The Senate is made up of 315 elected lawmakers. There are also seven senators appointed for life, but by tradition they do not take sides. For hours after the vote ended Monday, projections and returns swung dramatically back and forth between the two coalitions, and without the vote from abroad, the election's outcome remained unclear. Voter turnout was about 84%. 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 that 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," leading center-left lawmaker Luciano Violante said earlier in the day. Even with a slim majority in parliament's houses, a coalition would officially win. But it would find it extremely difficult to pass legislation, returning Italy to instability after Berlusconi's five years in power. If parliament is split between the two coalitions, the president 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 seemed unlikely. Still, politicians said that one possible solution to a legislative deadlock might be a grand-coalition government to handle urgent economic matters and the election of a new president - whose mandate expires in mid-May - with new parliamentary elections some time in the fall. "We have to immediately send a message to the markets, to whoever wants to invest in Italy that the country is not going to fall apart," said Culture Minister Rocco Buttiglione. Berlusconi, a 69-year-old media mogul who is Italy's longest serving premier since World War II, was battling to capture his third premiership 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 and EU chief, was making his comeback bid with a potentially unwieldy coalition of moderate Christian Democrats, Greens, liberals, former Communists and Communists. Italians were mainly preoccupied by economic worries. Berlusconi failed to jump start a flat economy during his tenure, but promised to abolish a homeowner's property tax. Prodi said he would revive an inheritance tax abolished by Berlusconi, but only for the richest; he also promised to cut payroll taxes to try to spur hiring. Still, the candidates seemed to hurl more insults at each other than comprehensive plans for turning around the economy. The premier's critics have accused him of having used his coalition's comfortable majority in parliament to push through laws to protect his business interests. He founded a business empire that expanded to include Italy's main private TV networks, the Milan soccer team, as well as publishing, advertising and insurance interests. Berlusconi, in turn, depicted Prodi as a front man for communists in a campaign to damage democracy. During his tenure, Berlusconi, a flamboyant billionaire, had strongly supported US President George W. 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.