Typhoon Vongfong, Japan's strongest storm this year, at 0500 GMT Saturday was about 150 km (94 miles) southeast of Naha City, the biggest city in Okinawa, and moving north at 15 kph (9 mph), Japan Meteorological Agency (JMA) said.
Its winds gusted up to 234 kph (146 mph). Fourteen people in Okinawa and Kagoshima prefecture in Kyushu were injured due to strong winds, the Mainichi newspaper reported.
It was likely to be closest to Okinawa - 1,600 km (1,000 miles) southwest of Tokyo, and the home of the largest contingent of US troops in Japan - on Sunday morning Japan time, local media reports said.
The typhoon was expected to weaken as it moved north, however, and likely to hit land on Monday morning on the westernmost main island of Kyushu, before moving northeast towards Japan's main island of Honshu on Tuesday.
All flights from and to Okinawa's Naha airport were canceled due to the airport's closure on Saturday, the airport said. About 27,000 homes have been affected by power outages, Okinawa Electric Power Co said.
There are no nuclear plants on Okinawa, but there are two on Kyushu and one on Shikoku island, which borders Kyushu and may be hit. Operations at all were halted, in line with national policy.
Vongfong, which means wasp in Cantonese, was following the path of Phanfone, a typhoon that slammed in Honshu on Monday, disrupting transport and prompting evacuation advisories for hundreds of thousands of people. Seven people were killed, including three US airmen swept out to sea and a man who died while surfing. REUTERS