A large and very strong typhoon is approaching Japan's southern prefecture of Okinawa. Officials are calling on people to be on the alert for violent winds, storm surges and high waves.

Japan's Meteorological Agency says that as of 5 a.m. on Wednesday, Typhoon Khanun was estimated to be at sea 80 kilometers southeast of the prefectural capital of Naha City. It was moving west-northwest at a speed of 15 kilometers per hour.

The storm was packing winds of up to 180 kilometers per hour near its center, and gusts of up to 252 kilometers per hour.

Officials say Typhoon Khanun is now very close to the Okinawa region.

Maximum wind speeds on Wednesday are expected to reach 134 kilometers per hour in the Okinawa region, and 90 kilometers per hour in the Amami region slightly farther north. Peak gusts could hit 234 kilometers per hour in Okinawa, and 126 kilometers in the area of the Amami Islands.

The typhoon is also likely to bring torrential rain accompanied by lightning in the regions. In the 24-hour period through Thursday midnight, as much as 200 millimeters of rain is expected in the Okinawa region, and 120 millimeters in Amami. More rainfall is likely through Saturday.

The officials are warning of flooding in coastal areas of the two regions due to storm surges expected at full tide.

They say Typhoon Khanun is forecast to slow down over the East China Sea, and that weather in the areas could be affected for a prolonged period.

The officials warn of landslides, flooding and swollen rivers. They are urging people to take shelter in sturdy buildings before the wind and rain grow stronger.