Storm-tracker Tropical Storm Risk listed Kalmaegi as a category 2 typhoon on a 1-5 scale with 5 the most severe and said it would grow to a category 3 storm by mid-Friday.

On Friday the typhoon will move north towards China, hitting the coast of Zhejiang province, Tropical Storm Risk said on its website, www.tropicalstormrisk.com.

Taiwan's weather bureau issued wind and rain warnings for greater Taipei, the northern port city of Keelung and three other counties. It also warned boats off the south and east coasts. Local TV said mudslides were likely in mountainous areas.

Schools and work were cancelled in some areas on Thursday afternoon as TV showed flooding in some areas.

"The weather bureau says the typhoon has covered central Taiwan northward, the northeast and the southeast," the island's Central News Agency said. "Rain is continuing and the south should be on guard for extremely heavy rain."

Typhoons regularly reach China, Taiwan, the Philippines and Japan from August until the end of the year, gathering strength from the warm waters of the Pacific or the South China Sea before weakening over land.

Krosa, the last typhoon to hit Taiwan, kept people indoors as work and classes were cancelled. Three people were injured in the early October storm. (Reporting by Ralph Jennings; Editing by Bate Felix)