US weather officials are describing a violent typhoon approaching Kyushu in southwestern Japan as a "super typhoon."

The Joint Typhoon Warning Center, or JTWC, said according to its analysis on Saturday Typhoon Nanmadol has strengthened. It has maximum winds exceeding 216 kilometers per hour.

Experts say in the United States a super typhoon is defined as a typhoon with a central atmospheric pressure of less than about 900 hectopascals and a maximum wind speed of 216 kilometers or more.

Japan's Meteorological Agency says Nanmadol had a central atmospheric pressure of 910 hectopascals on Saturday morning.

But it was a little short of the JTWC's criteria for a super typhoon, as it was packing winds of up to 198 kilometers per hour near its center.

Agency officials say the typhoon is maintaining its strength and describe it as extremely dangerous. They are urging people in the regions likely to be affected to be on the highest alert.