As many as eight million people have been asked to evacuate areas of Japan threatened by an approaching storm.
Typhoon Haishen is expected to intensify in the coming hours, bringing heavy rain, storm surges and winds of more than 100mph (160km/h).
On the south-western Kyushu island, at least 142,000 households have already been left without power.
The typhoon will move past Kyushu later on and is expected to make landfall on Monday in South Korea.
The country has raised its typhoon warning to the highest level.
Haishen comes days after Maysak, one of the region’s strongest typhoons in years.
Haishen has led to the closure of factories, schools and businesses across western Japan. Hundreds of flights and train services have also been cancelled.
Japan’s weather agency urged residents to exercise their “most serious caution” for possible record rains and high waves along the coast.
Yoshihisa Nakamoto, director of the agency’s forecast division, told reporters that surging tides may also cause flooding in low-lying areas, particularly around river mouths.
As a result of the storm, millions of people have been advised to move to designated shelters in places like schools and community centres.
But local media report that some people have chosen to seek safety in local hotels to reduce the risk of coronavirus spreading in crowded public shelters.
In South Korea, the Central Disaster and Safety Countermeasure Headquarters raised the country’s typhoon warning level to four – the highest – at 19:00 (10:00 GMT) on Sunday.
The Korea Forest Service also raised the landslide alert to its highest level.
Its chief, Park Chong-ho, told Yonhap news agency: “Huge damage is expected as the typhoon this time is forecast to be more dangerous than the previous ones that affected South Korea shortly after the end of the monsoon season.”
Typhoon Haishen is forecast to move close to Busan on Monday morning.
The typhoon has also forced Japan’s coast guard to suspend its search for missing sailors from a cargo ship that sank during Typhoon Maysak.
The Gulf Livestock 1 was carrying 43 crew members and 6,000 cows when it went missing on Wednesday.
Three crew members were rescued alive.