As least five people are reported dead and others are missing as Japan endures what could be its worst storm for 60 years.
The eye of Typhoon Hagibis made landfall shortly before 19:00 local time (10:00 GMT), in Izu Peninsula, south-west of Tokyo.
It is now moving up the eastern coast of Japan’s main island, with wind speeds of 225km/h (140mph).
More than 270,000 homes have lost power, Japanese outlet NHK reports.
Kyodo News agency said five deaths had been confirmed in different areas.
Two people died after homes were swept away by landslides – a man in Tomioka, Gunma Prefecture, and a woman in Sagamihara near Tokyo.
A man in his 60s was found dead in an inundated apartment in Kawasaki, south-west of Tokyo, while a woman fell into a waterway and drowned in Tochigi, Kyodo said. Another victim, a man in his 50s, was found dead in an overturned car in Chiba.
Kyodo said 11 people were reported missing and more than 90 had been reported injured.
More than seven million people have been urged to leave their homes amid severe flood and landslide warnings, but it is thought only 50,000 are staying in shelters.
“Unprecedented heavy rain has been seen in cities, towns and villages for which the emergency warning was issued,” JMA forecaster Yasushi Kajiwara told a press briefing.
Japan’s Meteorological Agency (JMA) has warned that half a metre of rain could fall on the Tokyo area between midday on Saturday and Sunday.
Many bullet train services have been halted, and several lines on the Tokyo metro were suspended for most of Saturday.
All flights to and from Tokyo’s Haneda airport and Narita airport in Chiba have been cancelled – more than a thousand in total.
Two Rugby World Cup games scheduled for Saturday were cancelled on safety grounds and declared as draws – England-France and New Zealand-Italy. The cancellations were the first in the tournament’s 32-year history.
Sunday’s Namibia-Canada match due to take place in Kamaishi was also cancelled and declared a draw.
The US-Tonga fixture in Osaka and Wales-Uruguay in Kumamoto will go ahead as scheduled on Sunday, organisers said.
Meanwhile, a crunch game between Scotland and tournament hosts Japan on Sunday is hanging on a safety inspection. Scotland have threatened legal action if it does not go ahead.
Formula 1 also postponed Saturday’s qualifying races for the Japanese Grand Prix “in the interests of safety for the spectators, competitors, and everyone at the Suzuka Circuit”.
Local resident James Babb spoke to the BBC from an evacuation centre in Hachioji, western Tokyo. He said the river near his house was on the brink of overflowing.
“I am with my sister-in-law, who is disabled,” he said. “Our house may flood. They have given us a blanket and a biscuit.”
Andrew Higgins, an English teacher who lives in Tochigi, north of Tokyo, told the BBC he had “lived through a few typhoons” during seven years in Japan.
“I feel like this time Japan, generally, has taken this typhoon a lot more seriously,” he said. “People were out preparing last night. A lot of people were stocking up.”
Only last month Typhoon Faxai wreaked havoc on parts of Japan, damaging 30,000 homes, most of which have not yet been repaired.
“I evacuated because my roof was ripped off by the other typhoon and rain came in. I’m so worried about my house,” a 93-year-old man told NHK, from a shelter in Tateyama, Chiba.
Hagibis means “speed” in the Philippine language Tagalog, and it could be the strongest storm the country has faced since Typhoon Vera in 1959.
Vera hit Japan with winds of 306km/h (190mph) and left more than 5,000 people dead or missing.
By Saturday afternoon local time, footage and pictures showed several rivers had breached their banks. They include the Tamagawa, which flows through residential areas of Tokyo.
“There were parts where the bank was not fully built. We had been dealing with it by sandbagging, but water started overflowing,” land ministry official Shuya Nakamura told the AFP news agency.
Many locals stocked up on provisions before the typhoon’s arrival on the authorities’ advice, leaving supermarkets with empty shelves.
Japan weathers about 20 typhoons a year, but Tokyo is rarely hit on this scale.
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