Sanae Takaichi's coalition is expected to win between 302 and 366 out of 465 seats in the chamber, national broadcaster NHK has predicted.
That is well above the 233 needed for a majority.
It comes after she called a rare winter snap election, seeking to capitalise on her own high approval ratings.
Betting on herself, Ms Takaichi, 64, pledged to secure a majority of step down.
She became Japan's first female prime minister in October after taking charge of the struggling Liberal Democratic Party (LDP), whose fortunes she is credited with transforming.
The lower house, or House of Representatives, is the stronger of the two chambers that comprise the National Diet - the Japanese equivalent of parliament.
A stronger hand there will empower her to make progress on her aims to boost Japan's economy and military while fostering closer ties with the US.
Ms Takaichi, a former heavy metal drummer, says her country is suffering from "foreigner fatigue" from immigration and tourism, and her nationalist rhetoric has stoked tensions with China.
She's anti gay marriage and a vocal defender of traditional gender roles, and sees late British prime minister Margaret Thatcher as a role model.
Her LDP party has grown accustomed to power, having governed almost continuously since its foundation in 1955, except for two brief windows - from 1993 to 1996, and from 2009 to 2012.
But the party has suffered setbacks in recent years, enduring its second worst electoral performance ever in 2024 amid a backdrop of a financial scandal and economic stagnation, and losing its majority in the lower house.
This breaking news story is being updated and more details will be published shortly.
Please refresh the page for the fullest version.
You can receive breaking news alerts on a smartphone or tablet via the Sky News app. You can also follow us on WhatsApp and subscribe to our YouTube channel to keep up with the latest news.
The 41-year-old American ruptured her ACL in a crash at a World Cup race in Switzerland on 30 January but was determined to compete at the Olympics nevertheless.
Just 13 seconds into her final run in Cortina, northern Italy, on Sunday, Vonn crashed on the piste, having clipped a slalom flag while mid-air.
The Team USA athlete was heard screaming after the crash as she was surrounded by medical personnel.
She was then strapped to a gurney and flown to hospital by helicopter.
The severity of her injuries is not known.
People in the crowd, including rapper Snoop Dogg, watched as the skier crashed and was taken away from the course.
Vonn's teammate, Breezy Johnson, was in the lead.
Vonn was considered a medal hopeful despite her ruptured ACL and completed two impressive training runs earlier this week.
She had returned to elite ski racing last season after nearly six years, having had a partial titanium knee replacement in her right knee.
As well as the ruptured ACL, she also had a bone bruise and meniscus damage.
This breaking news story is being updated and more details will be published shortly.
Please refresh the page for the fullest version.
You can receive breaking news alerts on a smartphone or tablet via the Sky News app. You can also follow us on WhatsApp and subscribe to our YouTube channel to keep up with the latest news.
The new yellow warning is for south England and large parts of South Wales, and lasts from 12pm on Monday to midnight.
Affected areas include Hampshire, Isle of Wight, Portsmouth, Southampton and West Sussex.
In South West England areas include Cornwall and Devon, with Swansea and Newport among affected areas in Wales.
The warning forecasts spray and flooding on roads "probably making journey times longer".
Bus and train services will probably be impacted with flooding of a few homes and businesses possible, it added.
There will also be a chance of some interruption to power supplies and other services, it continued.
Meanwhile, the Environment Agency has 88 flood warnings in place, mostly across southwest England and the East and West Midlands.
See the weather forecast in your area
There are also 223 flood alerts. A flood warning means flooding is expected, and an alert means flooding is possible.
The Met Office said on Thursday that rain had fallen every day of 2026 so far in southwest England and South Wales.
There has been 50% more rainfall than usual in both, the forecaster added.
Both have experienced a far wetter than average January, with 50% more rainfall than usual, the forecasters said.
Sarah Cook, Flood Duty Manager at the Environment Agency, said: "Our thoughts are with all those affected by the ongoing impacts of Storm Chandra, including those whose homes and businesses have sadly been flooded.
"Significant ongoing groundwater flooding impacts remain probable in parts of Dorset and Wiltshire, with minor impacts probable for parts of Hampshire for the next five days, and West Sussex from Saturday.
"Environment Agency teams are out on the ground, to reduce the impact of flooding and support those communities affected. We urge people not to drive through flood water - it is often deeper than it looks and just 30cm of flowing water is enough to float your car."
Officers in riot gear and with shields confronted about 100 protesters, some of whom wore hoods and scarves to cover their faces, after they broke away from a main demonstration and appeared to be trying to reach the Santagiulia Olympic ice hockey rink.
A group of protesters also set off smoke bombs and firecrackers about half a mile (800 metres) from the Olympic Village, where around 1,500 athletes are staying.
Six people were arrested during the altercation, according to police sources.
Around 10,000 people attended the main demonstration in Milan on Saturday, on the first full day of the Winter Olympics, to protest against the environmental, economic and social impact of the Games.
Read more: Follow all the updates from the Winter Olympics in Italy
'Serious sabotage' on the rails
Meanwhile, the train network in northern Italy was hit by an act of "serious sabotage", according to the country's Ministry of Transport.
Police reported three acts of sabotage at three different locations, leading to passenger delays of up to two-and-a-half hours.
Rail infrastructure near Bologna was damaged on Saturday, causing the city's high-speed station to temporarily close, as train journeys were disrupted on the first full day of the Winter Olympics.
A cabin, housing a track switch, was set on fire in an early-morning attack near Pesaro, on the Adriatic coast.
Several hours later, electrical cables used to detect train speeds were found severed in Bologna, while a rudimentary explosive device was discovered by a track at a nearby location.
Nobody has claimed responsibility for the incidents, which appeared to have been coordinated, a police spokeswoman said.
Deputy prime minister Matteo Salvini, who heads up the transport ministry, said of the attacks: "These actions of unprecedented seriousness do not in any way tarnish Italy's image in the world, an image that the games will make even more compelling and positive."
Olympic infrastructure projects criticised
The march was organised by grassroots unions, housing-rights groups and social centre community activists.
Protesters carried cardboard cutouts of trees to represent the trees that were felled to build the new bobsled run in Cortina for the Olympics, arguing that infrastructure projects like this have damaged the environment in mountain communities.
"They bypassed the laws that usually are needed for major infrastructure projects, citing urgency for the Games," one protester said, adding that he was concerned that the private company organising the event would eventually pass on debt to Italian taxpayers.
The International Olympic Committee argues that the Games largely use existing facilities, making them more sustainable.
Read more:
Opening ceremony crowd ignored plea not to boo
Olympics hit by penis enhancement controversy
Best pictures from the Olympics opening day
Police brought the splinter group of violent protesters under control before the main demonstration finished, according to Italian news agency ANSA.
'ICE out' signs
Some protesters said they were opposed to the deployment of US immigration and customs enforcement (ICE) agents to Italy to provide security to the US delegation of athletes, following previous protests in the buildup to the Games.
US Homeland Security Investigations, an ICE unit that focuses on cross-border crimes, often sends officers to events abroad like the Olympics to help with security.
The ICE unit used to crack down on immigration in the US is known as Enforcement and Removal Operations, and there is no indication its officers have been deployed to Italy.
Nancy Guthrie was last seen at her own home near Tucson, Arizona, on the evening of 31 January, and was reported missing the next day after she did not turn up at church.
Law enforcement officials have concluded that she was kidnapped, but the Pima County Sheriff's Department said it has not identified any suspects or people of interest in the case.
On Saturday, a week after her mother's disappearance, the NBC News Today co-anchor posted a video on Instagram where she urged those believed to be holding Ms Guthrie to return her.
"We received your message and we understand," she said, joined by her siblings Cameron and Annie. "We beg you now to return our mother to us, so that we can celebrate with her."
"This is the only way we will have peace," she added. "This is very valuable to us, and we will pay."
Savannah Guthrie was referring to a message sent to the Tucson-based television station KOLD on Friday, according to Kevin Smith, a spokesperson for the FBI office in Phoenix.
KOLD said it received an email related to the Guthrie case on social media that day but declined to share details about its contents as the FBI conducted its review.
The station was one of several news outlets that received alleged ransom letters during the week.
Sky's US correspondent Martha Kelner said that "this is obviously a huge mystery still", noting that there are "no suspects and no persons of interest in this case".
While it's still unclear who the sender is, she added it appears they "used the same secure server to hide their IP address" and that the new note "the senders believe will indicate to investigators that they are the same person or people that sent the original note".
Read more from Sky News:
Gordon Brown says he was 'betrayed' by Mandelson
Dozens of flood warnings issued in UK
It comes after it emerged that police investigating Ms Guthrie's disappearance were searching for a vehicle or vehicles that may be connected to her case.
A spokesperson for the convenience store chain Circle K told NBC News on Friday that officers visited one of their stores after "receiving a tip regarding a vehicle of interest, and our team has provided them access to the store's surveillance video".
Sky News has contacted the Pima County Sheriff's Department for comment.