Typhoon Haishen hits Japan on Sunday, bringing in its wake violent winds gusting up to 216 km (135 miles) and heavy rains.
Japan Meteorological Agency predicted "record-level rainfall, landslides, and floods. Surging tides are expected to cause flooding in low-lying areas, particularly around river mouths.
After lashing a string of exposed, remote southern islands, Haishen neared Japan's Kyushu region on Sunday evening, with authorities issues evacuation advisories for more than seven million residents.
As the storm passed over several remote islands earlier Sunday, strong winds bent palm trees and sheets of rain lashed the area.
Earlier, at an emergency cabinet meeting, Prime Minister Shinzo Abe warned that flooding and landslides were a possibility.
"Maximum caution is needed as record rain, violent winds, high waves, and high tides are possible," he said.
"I ask the Japanese people, including those who live in high-risk areas for flooding rivers or high tides, to stay informed and take action immediately to ensure their safety," he added.
At 7 pm (1000 GMT), Haishen was located about 100 kilometers (62 miles) south-southwest of Makurazaki city.
The storm was forecast to move north and travel off the western coast of Kyushu before reaching South Korea Monday morning, according to the weather agency.
Authorities issued evacuation orders for 1.8 million people in the affected area, with 5.6 million people issued lower-level advisories, national broadcaster NHK said.
Evacuation orders in Japan are not compulsory, though authorities strongly urge people to follow them.
Local officials asked people to avoid crowded shelters where possible, to reduce the risk of coronavirus infections, and some shelters were forced to turn people away in order to have enough space to maintain social distancing.