Okinawa, Japan (BBN)-Hundreds of thousands of people have been urged to seek shelter as a powerful typhoon passes over Japan's Okinawa island chain.

Typhoon Neoguri was due to pass over Okinawa's main island later on Tuesday, with strong winds and torrential rain.

Flights have been cancelled and schools shut. Local television footage showed palm trees being tossed by wind.

Forecasters said the storm could be one of the strongest to hit Japan, generating waves up to 14m (46ft).

"There is a risk of unprecedentedly strong winds and torrential rains. Please refrain from non-essential outdoor activities,'' Japan Meteorological Agency (JMA) spokesman Satoshi Ebihara told a news conference on Monday night.

Local authorities urged some 480,000 residents across Okinawa to stay at home or move to community centres for shelter.

More than 50,000 households were reported to be without power, and one oil refinery has halted operations.

As of 12:00 local time (04:00 GMT), Typhoon Neoguri was reported to be heading north at a speed of 25 kilometres per hour (15 mph), with gusts of up to 252 kilometres per hour (151 mph), Kyodo news agency reported.

Residents have been bracing themselves for rough weather.

Kathryn Spoor, who lives in Okinawa, told the BBC that most of the people who needed to evacuate had done so already.

"Right now we do have a lot of wind and rain," she said. "We have showers coming in and gusts in my area are at about 143 kilometres per hour right now so it is definitely a dangerous situation."

Okinawa, Japan's southern-most prefecture that comprises several islands, is home to major US bases. Around 26,000 US troops are stationed there under a long-standing security alliance.

Officers have evacuated some aircraft from Kadena Air Base in preparation for Typhoon Neoguri's arrival.

Lieutenant Erik Anthony, near Kadena Air Base, said winds were starting to pick up.

"Trees are bending and you can see branches flying across the street, garbage and trash rolling down the road," he told the BBC.

"But I haven't seen any major damage as of yet and the communication is still up, which is a huge priority here on Okinawa.

Urging residents to remain on maximum alert, JMA warned of the possibility that Typhoon Neoguri could move north to Japan's main island of Honshu.

BBN/ANS-08July14-11:00am (BST)