Japan's hawkish ex-premier Shinzo Abe will get a second chance to run the country after his conservative Liberal Democratic Party (LDP) surged to power, but must swiftly move to bolster the sagging economy while managing strained ties with China.

Abe, whose party won by a landslide just three years after a crushing defeat, was expected to meet Natsuo Yamaguchi, the leader of the small New Komeito party, to cement their alliance and confirm economic steps to boost an economy now in its fourth recession since 2000.

The victory by the LDP, which had ruled Japan for most of the past 50 years before it was ousted in 2009, will usher in a government pledged to a tough stance in a territorial row with China, a pro-nuclear energy policy despite the 2011 Fukushima disaster and a potentially risky recipe for hyper-easy monetary policy and big fiscal spending to boost growth.

Projections by TV broadcasters showed that the LDP had won at least 291 seats in the 480-member lower house, while the New Komeito party took at least 29 seats.

That gives the two parties the two-thirds majority needed to overrule parliament's upper house in most matters, where they lack a majority and which can block bills.

The "super majority" could help to break a policy deadlock that has plagued the world's third biggest economy since 2007.

Markets have already pushed the yen lower and share prices higher in anticipation of an LDP victory and Abe's economic stimulus. The two-thirds "super majority" could boost share prices and weaken the yen further.

Prime Minister Yoshihiko Noda's Democratic Party of Japan (DPJ) was crushed, forecast to win just about 56 seats - less than a fifth of its showing in 2009, when it swept to power promising to pay more heed to consumers than companies and pry control of policies from bureaucrats.

But voters deemed the pledges honoured mostly in the breach and the party was hit by defections before the vote due to Noda's unpopular plan to raise the sales tax to curb public debt already more than twice the size of the economy.

"This was an overwhelming rejection of the DPJ," said Gerry Curtis, a professor at New York's Columbia University.

"Abe was smart to run the campaign saying 'It's the economy, stupid. His hawkish (security) views took second place to fiscal stimulus and getting a dovish Bank of Japan governor and getting the economy going. If he keeps that focus ... he has a chance of improving his standing."

Analyst Bruce Klingner of the Heritage Foundation think tank in Washington said the return of Abe and LDP was foremost a rejection of the DPJ, but "also reflects an embrace of conservative views" after recent years of strained relations with Japan's close neighbours.

"Chinese assertiveness and North Korean provocations nudged the public from its usual post-war complacency toward a new desire to stand up for Japanese sovereignty," he said.

The Japanese favour moving toward "a more normal nation status" and are not embracing resurgent militarism, added Klingner, a former CIA analyst.

Abe, expected to be voted in by parliament on December 26, will also have to prove he has learned from the mistakes of his first administration, plagued by scandals and charges of incompetence.

Voter distaste for both major parties has spawned a clutch of new parties including the Japan Restoration Party, founded by popular Osaka Mayor Toru Hashimoto, which took at least 52 seats, according to media projections.

But media estimates showed turnout at around 59 per cent, which could match the previous post-war low.

LDP leader Abe, 58, who quit as premier in 2007 citing ill health, has been talking tough in a row with China over uninhabited isles in the East China Sea, although some experts say he may temper his hard line with pragmatism once in office.

The soft-spoken grandson of a prime minister, who will become Japan's seventh premier in six years, Abe also wants to loosen the limits of a 1947 pacifist constitution on the military, so Japan can play a bigger global security role.

President Barack Obama congratulated Abe and underlined US interest in working with the longstanding American ally.

"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," he said in a statement.

The LDP, which promoted atomic energy during its decades-long reign, is expected to be friendly to nuclear utilities, although deep public concerns remain over safety.

Abe has called for "unlimited" monetary easing and big spending on public works to rescue the economy. Such policies, a centrepiece of the LDP's platform for decades, have been criticised by many as wasteful pork-barrel politics.

Many economists say that prescription for "Abenomics" could create temporary growth and enable the government to go ahead with a planned initial sales tax rise in 2014 to help curb a public debt now twice the size of gross domestic product.

But it looks unlikely to cure deeper ills or bring sustainable growth to Japan's ageing society, and risks triggering a market backlash if investors decide Japan has lost control of its finances.