Storm Jangmi -- which was downgraded from a typhoon -- injured 15 people in southern Japan on Tuesday, knocked out power to thousands of homes and grounded hundreds of flights.

Authorities have warned of further disruption on Wednesday, with possible transport delays in Tokyo, while some schools in the capital have closed.

Japan's two biggest airliners All Nippon Airways and Japan Airlines cancelled a combined 616 flights -- including 92 international flights -- scheduled for Wednesday.

Around 370,000 people across a swath of the country from Shikoku island in western Japan to Tokyo have been urged to evacuate, the government said in a statement.

As of 6:00 am Wednesday (2100 GMT Tuesday), there was no new report of injuries but six buildings were partially destroyed.

Torrential rain filled rivers in western and eastern Japan including in the Tokyo area, with the Japan Meteorological Agency issuing flood warnings for regions including densely populated Aichi prefecture in central Japan and Tokyo.