Fresh off a decisive election victory, Japan's leader pledges to tackle what he calls Japan's two national crises: the military threat from North Korea, and an aging and declining population.

Shinzo Abe, re-elected as prime minister, said at a news conference that he is committed to protect the Japanese people's prosperity and peace from any contingency. He also referred to Japanese people who were abducted years ago and are believed to still being held by North Korea.

"I will pursue decisive and strong diplomacy to tackle North Korea's missile, nuclear and abduction issues and put further pressure to get it to change its policy," he said.

His ruling coalition was returned to power in elections for Japan's more powerful lower house Sunday.

Abe said Japan's decreasing population and aging is "the biggest challenge" for his "Abenomics" policy aimed at Japan's economic recovery from deflation. "The problem is progressing by the minute, and we cannot afford waiting around."

He promised a comprehensive package by the end of the year to deal with Japan's demographic challenges, including investments in education, productivity improvements and pension system reform.

Abe's Liberal Democratic Party and a small coalition partner together secured at least 313 seats in the 465-member lower house, passing the 310-barrier for a two-thirds majority. Three seats remained undecided.

Abe said the result showed "strong support" from the people and thanked them for backing stability and his government's policies.

RUSSIA-JAPAN/

Sailors with Japan's Maritime Self-Defence Force stand on the deck of a training ship as they arrive in Vladivostok, Russia, on Oct. 14. Japan's post-war Constitution renounces the use of force in international conflicts and limits Japan's military to self-defence. (Yuri Maltsev/Reuters)

The victory boosts Abe's chances of winning another three-year term next September as leader of the LDP. That could extend his premiership to 2021, giving him more time to try to win a reluctant public over to his longtime goal of revising Japan's pacifist Constitution.

In the immediate term, the win likely means a continuation of the policies Abe has pursued since he took office in December 2012 — a hard line on North Korea, close ties with Washington, including defence, as well as a super-loose monetary policy and push for nuclear energy. Stocks rose in Tokyo on Monday morning.

Abe said he will have "deep discussion" on North Korean policies with U.S. President Donald Trump during his planned Nov. 5-7 visit in Japan. Abe said he will call a special parliamentary session to be re-elected as prime minister and install his new cabinet, which is expected to retain most of its current members.

Abe's ruling coalition already has a two-thirds majority in the less powerful upper house. Having a so-called supermajority in both houses gives them virtually a free hand to push even divisive policies and legislation.

That would also increase Abe's chances for achieving a constitutional revision, a goal his party and its nationalist supporters have advocated for years. They view the 1947 constitution as the legacy of Japan's defeat in World War II and an imposition of the victor's world order and values.

The charter renounces the use of force in international conflicts and limits Japan's troops to self-defence, although Japan has a well-equipped modern military that works closely with the U.S.

JAPAN-ELDERLY/

Elderly and middle-age people exercise during Respect for the Aged Day in Tokyo on Sept. 18. Abe said Japan's decreasing population and aging are 'the biggest challenge' for his economic policy. (Toru Hanai/Reuters)

Any change to Japan's Constitution, which has never been amended, requires approval first by two-thirds of parliament, and then in a public referendum. Polls indicate that the Japanese public remains opposed to amendment.

The win indicates Abe has bounced back from the summer, when support ratings for his cabinet plunged to 30 per cent after accusations of government favouritism to people connected to him. For the first time since he took office nearly five years ago, he appeared vulnerable as both party leader and prime minister.

The ruling coalition's victory reflects as much the lack of viable alternatives as support for Abe. Turnout was just 54 per cent, as typhoon rains lashed much of the country and delaying final results.

Abe dissolved the lower house less than a month ago, forcing the snap election. Analysts saw it as an attempt to solidify his political standing at a time when the opposition was in disarray and his support ratings had improved somewhat.

His plan was briefly upstaged by the launch of a new opposition party by populist Tokyo Gov. Yuriko Koike. But initial excitement faded, and the Party of Hope took only 49 seats.

Another new party, the constitutional Democratic Party of Japan, won 55 seats and looks to be the biggest opposition grouping. It is liberal-leaning, while both the Party of Hope and Abe's Liberal Democratic Party are more conservative.