Japan's conservative opposition swept to victory in national polls on Sunday, giving former Prime Minister Shinzo Abe a second chance to push his hawkish security agenda and reflate the economy.

Voters dumped 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).

Noda said he would be resigning his party leadership in the wake of the drubbing.

But with turnout at a record low and voters complaining of no real choice, Abe acknowledged the result was not a ringing endorsement.

"This doesn't mean confidence in the LDP has been fully restored," Abe said.

"I think this result means a 'no' to the political confusion of the DPJ. People will be strictly watching if the LDP will be able to live up to expectations."

Abe spent the campaign pledging to bolster Japan's defences and stand up to China in a dispute over the sovereignty of a small chain of islands in the East China Sea.

As the results came in, he showed no signs of rowing back.

"China is challenging the fact that (the islands) are Japan's inherent territory," he said. "Our objective is to stop the challenge. We don't intend to worsen relations between Japan and China."

The 58-year-old, whose first stint as premier in 2006-7 ended ignominiously, has 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 that left the countryside riddled with underused bridges and roads to nowhere.

TV Asahi, citing forecasts based on both official results and its own exit polls, said the LDP had won at least 291 seats against 56 seats secured by the DPJ.

Together with New Komeito, its junior coalition partner, the LDP has the two-thirds majority of the 480-seat powerful chamber, enough to override the upper house in which no party has overall control, the television network said.

US President Barack Obama congratulated Abe on his party's success Sunday, saying he looked forward to working with the next government.

"The US-Japan Alliance serves as the cornerstone of peace and prosperity in the Asia-Pacific and I look forward to working closely with the next government and the people of Japan on a range of important bilateral, regional and global issues," Obama said in a statement.

He also expressed his appreciation to Noda for his "many contributions to US-Japan relations."

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.

Tetsuro Kato, politics expert at Hitotsubashi University, said the results showed the voter's deep disappointment with the DPJ over the past three years.

"It's not a landslide for the LDP but a crushing defeat for the DPJ," he added.

"So-called non-affiliated voters had no parties to cast their ballots for. Even if they did, their votes were divided."

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.

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 islands at the centre of the dispute with Beijing sparked months of tensions, secured a seat as leader of the third largest party.

His rabble-rousing Japan Restoration Party won between 46 and 61 seats, NHK television 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.

As Abe's victory became apparent, China's official news agency Xinhua urged Japan to reformulate its foreign policy.

"Instead of pandering to domestic hawkish views and picking fights with its neighbours, the new Japanese leadership should take a more rational stand on foreign policy," it said.

A humbled Noda was contrite, acknowledging he had led his troops to a stinging defeat, which also saw several cabinet ministers unseated.

"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.

"Politicians must take responsibility for results. The biggest responsibility for such a severe defeat lies with me as the party leader."