The government of Prime Minister Yoshihiko Noda was predicted to get a drubbing from an electorate that observers said would be handing the reins reluctantly to the Liberal Democratic Party (LDP).

Hawkish one-time PM Shinzo Abe appeared set for a return to office, after a campaign in which he has sketched out a harder line on foreign policy, as tensions rise with China over disputed islands in the East China Sea.

Abe, whose brief stint as premier in 2006-7 ended ignominiously, has pledged to right Japan's listless economy, which has suffered years of deflation, made worse by a soaring currency that has squeezed exporters.

"With stronger monetary policies, fiscal policies and growth policies, we will end deflation, correct a high yen, and grow the economy," he said in a Saturday stump speech.

He has also pledged to boost spending on infrastructure projects at a time when large parts of the tsunami-ravaged northeast have yet to see significant rebuilding following the March 2011 catastrophe.

The collapse of an ageing highway tunnel that claimed nine lives earlier this month lent credence to his calls, which have been criticised by opponents as a return to the LDP's "construction state" of the last century.

Public unease about a deteriorating security environment -- North Korea lobbed a rocket over Japan's southern islands last week and China sent a plane into Japanese airspace -- has bolstered Abe's cause.

He has promised to boost defences and re-anchor a security alliance with the United States that is widely thought to have drifted under Noda's Democratic Party of Japan (DPJ).

The DPJ disappointed electors who handed it a hefty majority in 2009 polls. Policy missteps, diplomatic gaffes and vicious factional infighting saw it burn through three premiers in as many years and squander its electoral hand.

A plodding and sometimes confused response to the disaster at Fukushima where nuclear reactors went into meltdown after the tsunami last year did it no favours either.

Opinion polls show that despite a strong anti-nuclear feeling in Japan, an array of smaller parties promising an atomic exit may struggle to get much traction.

But commentators say there is little enthusiasm for any party, and the LDP's likely victory will come from their perceived status as the least-worst option.

Polls are open for 13 hours from 7 am (2200 GMT Saturday).

Broadcasters' exit polls are expected to give a reasonable indication of the final outcome shortly after the ballot boxes are sealed.