Severe tropical storm Shanshan, now in waters south of Japan, is expected to move northward and approach the country's main islands from Tuesday.

The Japan Meteorological Agency says that as of 3 a.m. on Saturday, the storm had a central atmospheric pressure of 985 hectopascals and was packing maximum sustained winds of 108 kilometers per hour near its center, with peak gusts of 162 kilometers per hour.

Shanshan is forecast to develop and reach waters near the Ogasawara Islands before heading northwest. It is likely to strengthen by Tuesday and approach western and eastern Japan.

Officials say rain and winds may gradually become stronger, mainly on the Pacific side of western and eastern Japan.

They say northern Japan could also see rough weather from Wednesday onwards.

Central Japan Railway Company may cancel services on the entire Tokaido Shinkansen bullet train line, or some sections, for a period including Tuesday and Wednesday.

The firm may also halt local trains in and around the city of Nagoya.

West Japan Railway Company says the Sanyo Shinkansen bullet train line may be wholly or partially suspended from Tuesday through Wednesday.

The two firms are calling on travelers to check the latest information.