TOKYO—At least 20 people were injured and more than 10,000 were advised to evacuate in Japan’s Okinawa prefecture Saturday, with typhoon Vongfong set to make landfall late at night before churning toward the nation’s main islands.

Typhoon Vongfong, characterized as extremely strong by the Japan Meteorological Agency, was bringing maximum sustained winds of 162 kilometers per hour (100 miles an hour).