Severe tropical storm Shanshan is expected to approach Japan's main islands early next week.

The Japan Meteorological Agency says the storm is traveling northward in the Pacific. It says Shanshan was packing maximum sustained winds of 108 kilometers per hour near its center and gusts reaching 162 kilometers per hour as of 3 p.m. on Friday.

The storm's future course and strength have not yet been precisely determined.

Shanshan is expected to reach waters near the Ogasawara Islands on Saturday and approach western and eastern Japan on Tuesday or later.

Forecasters also say rain and winds may gradually become stronger mainly in the Pacific side of western and eastern Japan.

The officials say northern Japan could also see rough weather from Wednesday.

The operator of Japan's Tokaido Shinkansen bullet train says it may cancel services on the entire line or some sections for a period including Tuesday and Wednesday, depending on the course and strength of the storm.

The operator of the Sanyo Shinkansen says it may do the same.