Prime Minister Shinzo Abe's ruling coalition is set to retain a two-thirds majority in Sunday's general election, gaining a further mandate after five years in power and offering the bloc the impetus to pursue a first-ever amendment to the Japanese Constitution.

A divided opposition and low turnout likely contributed to the outcome of the election, which followed a rough year for Abe amid allegations of cronyism.

The victory could reinforce Abe's chances of succeeding in the Liberal Democratic Party leadership contest in September next year and eventually becoming Japan's longest-serving prime minister.

The significance of the two-thirds majority enjoyed by the coalition of the LDP and the smaller Komeito party is that it is required in both Diet houses to formally propose a constitutional revision, which must then gain a majority of votes in a national referendum.

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"The matter should be debated in the Diet, and at the same time I expect discussions to deepen among the public," Abe told a television program as results came in.

On its own, the LDP has secured a stable majority, defined as at least 261 of the House of Representatives' 465 seats, with which it can control all the house's legislative committees.

The election saw the opposition vote split between the Constitutional Democratic Party of Japan and the Party of Hope, new parties formed shortly before the start of campaigning out of the respective liberal and conservative wings of the collapsing Democratic Party.

The CDPJ came out on top among the opposition parties, having rapidly built support over the course of the campaign.

Led by former Chief Cabinet Secretary Yukio Edano, the CDPJ absorbed the Democratic Party's liberals who could not or would not join the "reform conservative" Party of Hope led by Tokyo Gov. Yuriko Koike.

The Party of Hope failed to maintain the excitement that greeted its formation late last month. It did poorly in single-seat districts in Tokyo -- thought to be its stronghold -- losing in 22 of the 23 districts in which it fielded candidates.

Koike, who broke from the LDP to run for Tokyo governor last year, had refused to resign as governor to run for the lower house with her new party. This meant voters were unsure who the party would back as prime minister in the event it formed a government.

Both opposition parties promised to freeze the consumption tax hike planned for October 2019 and abandon nuclear power. Neither had the time or resources to put up candidates in all of the 289 single-seat electoral districts.

Final voter turnout was expected to stand at around 54 percent, up slightly from the record postwar low of 52.36 percent in the last lower house election in 2014, according to Kyodo News estimates.

Rain and wind from Typhoon Lan battered much of the country on Sunday, discouraging voters and likely working in the ruling coalition's favor.

With local authorities encouraging early voting in light of the typhoon, a record high of 21 million people, or around 20.1 percent of the eligible population, cast their ballots early. The number of early votes leapt 62.5 percent from the figure in the last election.

Abe is expected to be voted back in as prime minister during a special Diet session to take place as soon as Nov. 1.

As part of the LDP's election platform, it pledged to include in forthcoming debate on constitutional reform the idea of adding an explicit mention of Japan's Self-Defense Forces. The SDF's status is currently not mentioned in the Constitution, by Article 9 of which Japan renounces war and the maintenance of "war potential."

While Komeito, the Party of Hope and the smaller Japan Innovation Party are all in favor of amendment, they differ on which changes should be prioritized.

A total of 1,180 candidates vied for the lower house's 465 seats, 289 of which represent single-seat electoral districts. The remaining 176 are filled through proportional representation, based on voters' preferred parties across 11 regional blocks.

Electoral reforms have reduced the size of the house to a postwar low. It had 475 seats before it was dissolved.

The LDP held 290 seats before campaigning began on Oct. 10, while Komeito had 35.

Dissolving the house on Sept. 28 for a snap election, Abe said he needed to secure a fresh mandate from the public for his administration's plans for the revenue from a consumption tax hike and for its handling of the threat from North Korea.

But the move appeared timed to take advantage of disarray among the opposition. It also allowed Abe to shelve a fall parliamentary session that would have seen him questioned again about the allegations that have damaged his reputation this year.

Sunday's election was the first lower house race in which 18- and 19-year-olds voted, after a law change took effect last year.