Japanese Prime Minister Shinzo Abe swept to a resounding victory in a snap election Sunday and immediately vowed to "deal firmly" with threats from North Korea that dominated the campaign.

Abe's ruling conservative coalition was on track to win more than 310 seats in the 465-seat parliament, according to a projection from public broadcaster NHK, handing the premier a two-thirds "super-majority."

This allows nationalist Abe to propose changes to pacifist Japan's US-imposed constitution, which forces it to renounce war and effectively limits its military to a self-defence role.

Abe said the comfortable election win had stiffened his resolve to tackle North Korea's nuclear threat, as the key US regional ally seeks to step up pressure on Pyongyang after it fired two missiles over Japan in the space of a month.

"As I promised in the election, my imminent task is to firmly deal with North Korea," said Abe, who is now on course to become the country's longest-serving leader.

"For that, strong diplomacy is required," stressed the 63 year-old, who has courted both US President Donald Trump and Russian President Vladimir Putin.

Abe said he would "deepen" debate on the divisive constitution issue in parliament but stressed: "I don't plan to propose (changes) via the ruling bloc alone. We'll make efforts to gain support from as many people as possible."

As results came in, television images showed jubilant victorious lawmakers bowing deeply before punching the air with cries of "Banzai", the Japanese equivalent of three cheers.

- 'Very severe result' -

Millions of Japanese braved torrential rain and driving winds to vote as a typhoon lashed the country, with many heeding warnings to cast their ballots early.

"I support Abe's stance not to give in to North Korea's pressure," said Yoshihisa Iemori as he cast his ballot in a rainswept Tokyo.

Abe's Liberal Democratic Party (LDP) benefited from a weak and splintered opposition, with the two main parties facing him created only a matter of weeks ago.

Support for the Party of Hope founded by popular Tokyo Governor Yuriko Koike fizzled after an initial blaze of publicity and was on track to win around 50 seats, according to the NHK projection with a handful still to call.

Speaking from Paris where she was attending an event in her capacity as leader of the world's biggest city, a sullen-faced Koike said it was a "very severe result."

"As the person who launched the party, I will take responsibility," pledged Koike.

The new centre-left Constitutional Democratic Party fared slightly better than expected but still trailed far behind Abe with a projected 50 seats.

"The LDP's victory is simply because the opposition couldn't form a united front," political scientist Mikitaka Masuyama from the National Graduate Institute for Policy Studies, told AFP.

- 'Sink' Japan -

The short 12-day campaign was dominated by the economy and the global crisis over North Korea, which has threatened to "sink" Japan into the sea and engaged in a war of words with Trump.

Hawkish Abe stuck to a hardline stance throughout, stressing that Japan "would not waver" in the face of an increasingly belligerent regime in Pyongyang.

But many voters said reviving the once-mighty Japanese economy was the top priority, with Abe's trademark "Abenomics" growth policy failing to trickle down to the general public.

"Neither pensions nor wages are getting better... I don't feel the economy is recovering at all," said 67-year-old pensioner Hideki Kawasaki.

Although voters turned out in their millions to back Abe, he enjoys only lukewarm support and surveys showed his decision to call a snap election a year earlier than expected was unpopular.

"I totally oppose the current government. Morals collapsed. I'm afraid this country will be broken," said 84-year-old voter Etsuko Nakajima.

- 'I'm quite disappointed' -

Koike briefly promised to shake up Japan's sleepy political scene with her new party but she declined to run herself for a seat, sparking confusion over who would be prime minister if she won.

In the end the 65-year-old former TV presenter was not even in Japan on election day.

"I thought that I would vote for the Party of Hope if it's strong enough to beat the Abe administration. But the party has been in confusion ... I'm quite disappointed," said 80-year-old pensioner Kumiko Fujimori.

The campaign was marked by a near-constant drizzle in large parts of the country and rallies frequently took place under shelter and a sea of umbrellas.

But this did not dampen the enthusiasm of hundreds of doughty, sash-wearing parliamentary hopefuls, who have driven around in minibuses pleading for votes via loudspeaker and bowing deeply to every potential voter.

Source: AFP