TOKYO - A powerful typhoon sweeping towards southern Japan on Tuesday triggered the cancellation of hundreds of flights, with officials urging hundreds of thousands of people to seek shelter. Typhoon Khanun was packing maximum sustained wind speeds of 180 kilometres (112 miles) an hour as it crossed the Pacific Ocean towards the Okinawa region.  The Japan Meteorological Agency said the storm, which it described as “very strong”, was about 170 kilometres southeast of the regional capital of Naha at 0600 GMT. The centre of the typhoon was expected to brush past Okinawa late Tuesday or early Wednesday before crossing to eastern China later in the week. Cities across Okinawa advised more than 760,000 people to leave their homes as the weather agency warned waves of up to 12-metres (39-feet) high could pummel the group of islands. The typhoon was expected to bring fierce winds and heavy rain.