High winds and heavy rains were forecast for central and western Japan, around the city of Osaka, with up to 300 mm (12 inches) of rain expected in some areas by noon on Wednesday.

The storm was about 100 km southeast of the Kii Peninsula in Wakayama, about 450 km (280 miles) west of Tokyo, at 7:00 p.m. (1000 GMT), Japan's Meteorological Agency said.

The storm, which was moving northeast at about 15 km per hour, had maximum winds near its centre of up to 90 km an hour and was expected to weaken once it hit land.

"The time of any landfall depends on whether the storm veers west or east," said an agency official.

"At the earliest, it may come ashore sometime tonight. But if it veers east, landfall will be later, sometime early tomorrow."

Taiwan, which could be hit by two storms later this week, issued a warning to shipping vessels as tropical storm Bopha headed towards the island, threatening to lash the southeastern coast with heavy rains and strong winds as early as Wednesday.

Forecasters were also tracking the more distant Saomai, named in Vietnamese for a plant, which the London-based Tropical Storm Risk Web site (http://tsr.mssl.ucl.ac.uk/) said was the only one of the three storms to be at typhoon strength as of Tuesday.

Saomai, which intensified Tuesday to reach Class 2 strength, was projected to brush the northern part of Taiwan sometime on Thursday or Friday if it remains on its current path.

Tropical storms in the region gather intensity from warm water and can develop into storms that frequently hit Taiwan, Japan, the Philippines, Hong Kong and southern China during a season that usually lasts from early summer to late autumn.

Both Bopha and Saomai were expected to head into China, where state-run news agency Xinhua said 77 died last week from floods and landslides caused by tropical storm Prapiroon, which means "God of Rain" in Thai.

The Japanese Meteorological Agency official said it was unusual, but not unheard of, to have three typhoons in the same region at the same time.