Some 600 people evacuated to shelters in Okinawa and electricity was cut to nearly 200,000 homes, public broadcaster NHK said.

At least 386 flights were cancelled mainly in western Japan, according to public broadcaster NHK.

Nine people suffered minor injuries in storm-related accidents in Okinawa, but no one was feared dead, local officials said.

"The number may rise further as we are in the middle of sorting out figures," said Masatsune Miyazato, an official at the island's disaster-management office.

"People in Okinawa are used to typhoons but we are strongly urging them to stay vigilant," he told AFP.

The weather agency warned people across Japan to be on alert for strong winds, high waves, heavy rain.

"The typhoon is feared to bring record rainfalls and violent winds over large areas," agency official Yasushi Kajiwara told reporters.

"Please stay on alert, evacuate early and ensure your safety," the official said.

After raking the outlying islands, the typhoon is forecast to pick up speed and approach western Japan on Sunday, "with a very strong force," as it barrels over the mainland, he added.

There have already been heavy downpours in large areas of western and eastern Japan, including the capital, as the storm spurred a seasonal rain front.

Fishermen in Kagoshima bay, where the typhoon is expected to make landfall, were already making preparations, tying down their boats as Trami approached -- even as forecasters warned that another typhoon was following in Trami's course.

Angler Masakazu Hirase told AFP: "It's dreadful because we already know there's another typhoon after this one but you cannot compete with nature. We do what we can to limit the damage."

If the forecast holds, it will be the latest in a series of extreme natural events to strike Japan.

Western parts of Japan are still recovering from the most powerful typhoon to strike the country in a quarter of a century in early September. Typhoon Jebi claimed 11 lives and shut down Kansai Airport, the main regional airport.

Officials at Kansai were already making preparations, placing sandbags and warning that they may be forced to close the airport.

Deadly record rains also hit western Japan earlier this year and the country sweltered through one of the hottest summers on record.

Also in September, a magnitude 6.6 earthquake rocked the northern island of Hokkaido, sparking landslides and leaving more than 40 people dead. (AFP)