TOKYO  - Japan's conservative opposition swept to victory in national polls Sunday, giving former Prime Minister Shinzo Abe a second chance to promote his hawkish security agenda and reflate the economy.Voters decisively abandoned Prime Minister Yoshihiko Noda three years after his Democratic Party of Japan (DPJ) promised a change from more than half a century of almost unbroken rule by the Liberal Democratic Party (LDP).Abe, who spent the campaign pledging to bolster Japan's defences and stand up to China over disputed islands, secured a handsome majority for the LDP in the election for the powerful lower house of parliament, exit polls showed.Abe, whose brief stint as premier in 2006-7 ended ignominiously, has also vowed to rectify the listless economy after years of deflation, made worse by a soaring currency that has squeezed exporters. He also offered to boost spending on infrastructure at a time when much of the tsunami-wrecked northeast remains a shell of its former self.Abe's calls were criticised by opponents as a return to the LDP's "construction state" of the last century which left the countryside riddled with underused bridges and roads to nowhere. Prime Minister Yoshihiko Noda has conceded defeat and said he was stepping down as leader from his humbled governing party."I will resign as the head of the Democratic Party of Japan because I take this result seriously," he told a press conference. "I want to deeply apologise as I could not produce results." NHK television, citing forecasts based on its own exit polls, said the LDP had won 275 to 310 seats in the 480-seat lower house, with the DPJ reduced to a rump of between 55 and 77 seats. It won more than 300 seats in the 2009 poll. New Komeito, LDP's junior coalition partner, had 27 to 35 seats, NHK said.That could give the pair a more than two-thirds majority in the powerful lower house, enough to override the upper chamber in which no party has overall control."The LDP sweeps to victory; Abe administration to start," the online edition of the Nikkei newspaper said in a banner headline.Analysts say the LDP's victory has come by default, with voters disenchanted by the DPJ after three years of flip-flops, policy missteps and diplomatic drift, but having little faith in any of the alternatives.Voter turnout, measured half an hour before the polls closed, was 45.42 percent, down more than seven points on the last election.  In the first national ballot since the tsunami-sparked meltdowns at Fukushima in March 2011, nuclear power had looked set to play a significant role. But an array of smaller parties promising an end to atomic generation made little impression on voters.The LDP says it will review all nuclear reactors in three years to decide whether to restart them.Nationalist former Tokyo governor Shintaro Ishihara, whose bid to buy the disputed islands provoked a fierce diplomatic showdown with China, secured a seat as leader of the third largest party.His populist Japan Restoration Party won between 40 and 61 seats, NHK said, giving him weight enough to shout from the parliamentary sidelines.Public unease about a worsening security environment - North Korea lobbed a rocket over Japan's southern islands last week and China sent a plane into Japanese airspace - bolstered Ishihara and Abe.The LDP has promised to revitalise a security alliance with the United States that is widely thought to have drifted under Noda's party. Hours before polls closed Chinese state media urged a post-election Japan to "devise its foreign policy with a long-term and pragmatic" view so Japan can "repair its strained ties with neighbours".Yasuko Kono, professor of politics at Hosei University in Tokyo, said the LDP had done better than anyone expected."The results are a harsh verdict by voters on the DPJ government. The big win is likely to guide the LDP coalition to a course to stability in power."Parliament will be called into session as early as December 26th to name Abe as the new prime minister, the Nikkei newspaper said.In an evening of misery for Noda, TV Asahi reported at least two of his ministers would lose their seats.Internal Affairs Minister Shinji Tarutoko and Education Minister Makiko Tanaka appeared to have lost their constituency seats. It is possible that they may win through on the proportional representation part of the ballot.Noda's own fate as leader of the much-diminished DPJ was also in doubt, despite his apparently having retained his seat.Kohei Otsuka, a senior party official told NHK: "In general, (Noda) can't help but take responsibility for (the defeat). But he will consider how to take responsibility."