Japan Prime Minister Shinzo Abe's ruling bloc is headed for a big election win, bolstering his chance of becoming the nation's longest-serving premier and re-energising his push to revise the pacifist constitution.
Abe's Liberal Democratic Party-led (LDP) coalition has won a combined 310 seats, reaching a two-thirds "super majority" in the 465-member lower house, with 11 seats still up for grabs, broadcaster TV Asahi said on Sunday.
A hefty win raises the likelihood that Abe, who took office in December 2012, will have a third three-year term as LDP leader next September and go on to become Japan's longest-serving premier. It also means his "Abenomics" growth strategy centred on the hyper-easy monetary policy will likely continue.
Final official results from the election, which coincided with an approaching typhoon, are expected early on Monday.
The US-drafted constitution's Article 9, if taken literally, bans the maintenance of armed forces. But Japanese governments have interpreted it to allow a military exclusively for self-defence.
Backers of Abe's proposal to clarify the military's ambiguous status say it would codify the status quo. Critics fear it would allow an expanded role overseas for the military.
The LDP's junior partner, the Komeito, is cautious about changing the constitution, drawn up after Japan's defeat in World War Two. Several opposition parties favour changes, but don't necessarily agree on details.
Amendments must be approved by two-thirds of each chamber of parliament and then by a majority in a public referendum.
Abe had said he needed a new mandate to tackle a "national crisis" from North Korea's missile and nuclear threats and a fast-ageing population, and to approve his idea of diverting revenue from a planned sales tax hike to education and child care from public debt repayment.
He called the poll amid confusion in the opposition camp and an uptick in his ratings, dented earlier in the year by scandals over suspected cronyism and a perception he had grown arrogant after nearly five years in office.
Abe has backed US President Donald Trump's tough stance towards North Korea, which has test-fired missiles over Japan. Trump is to visit Japan next month.
Abe, 63, has already led the LDP and its partner, the Komeito, to four landslide wins since he took the helm of the party. But turnout has been low and the LDP has typically won with about 25 per cent of eligible votes. Others either stayed home or backed opposition parties.