Tropical Storm Trami battered Taiwan with strong winds and torrential rains on Wednesday, forcing authorities to close offices and call off nearly 200 international flights.

The Central Weather Bureau said although the storm, 100 kilometres (62 miles) north-northeast of Taipei at 0930 GMT, was likely to miss the island, it would generate more heavy rainfall in the day ahead.

The bureau urged the public to be vigilant as the storm could even produce "cloudbursts" -- more than 100 mm of rain per hour -- in some areas.

Persistent torrential rains could lead to landslides in mountainous areas and flooding, it warned.

The storm has dumped up to 400 mm (16 inches) of rain in some northern parts of the island since Tuesday, the bureau said, adding that the volume could surge to one metre (40 inches).

Trami, with gusts of up to 137 kilometres per hour, was moving west at a speed of 25 kilometres per hour, the bureau said.

The bureau categorised it as a tropical storm, but the Hong Kong Observatory upgraded it to a typhoon late Wednesday.

Due to strong winds and heavy rains, the Taoyuan airport in the north cancelled 195 international flights, according to the transport ministry.

All the flights and ferries between Taiwan and offshore islands were terminated while major train and high-speed rail services remained uninterrupted.

Officials at the bureau said the storm's impact may be felt mostly from Wednesday night through early Thursday morning, as it churned towards China's southeast Fujian province.

Financial markets were closed, while offices and schools in the north, the area mostly affected by the storm, shut down.

As part of the government's preventive measures, the defence ministry deployed around 2,000 soldiers in some areas prone to be hit by flooding and landslides, and placed another 50,000 on stand-by.

President Ma Ying-jeou cut an overseas trip short by one day, flying back to Taiwan from a visit to the Caribbean via a stopover in the United States.

Last month Typhoon Soulik battered Taiwan with torrential rain and powerful winds, leaving two people dead and at least 100 injured.

Roofs were ripped from homes, debris and fallen trees littered the streets and some areas were submerged by floods.