Typhoon Saola, has killed at least 23 people in the Philippines, has already been blamed for four deaths in Taiwan, with the toll expected to rise. 

The slow-moving typhoon spawning torrential rains slammed into eastern Taiwan early Thursday (local time), flooding farmlands, disrupting transportation and turning the normally bustling capital of Taipei into a ghost town.

The storm made landfall near the eastern coastal city of Hualien just before daybreak, before veering northward and hugging the coast.

It was expected to pass near the northern port city of Keelung and skirt the Taipei suburbs by midday.

Packing sustained winds of 118 kilometres per hour and gusts of 155 kph, Saola's slow speed - only 12 kph - made it a virtual certainty that the heavy rains inundating northern Taiwan for the past 48 hours would continue through the weekend.

That raised the prospect of potentially devastating flooding in areas that have already absorbed more than 1,000 millimetres of rain since Tuesday.

Authorities ordered offices and businesses closed throughout northern Taiwan, including in Taipei.

Normally busy streets in the capital were deserted during the morning rush hour, as cleanup crews laboured to clear them of hundreds of trees and branches felled during the night by Saola's ferocious approach.

Television footage showed acre upon acre of flooded farmland in low-lying coastal areas, punctuated by scenes of raging rivers and roads blocked by mudslides in the island's mountainous centre.

The Defence Ministry mobilized 48,000 soldiers to help mitigate the storm's impact, dispatching many to help hard-pressed farmers try to save threatened fruit and vegetable harvests. 

Dozens of flights were cancelled at Taipei's main international airport, and rail transport throughout the island was disrupted.

The typhoon left at least 23 people dead in the Philippines and forced 180,000 to flee their homes in the capital, Manila, and 27 central and northern provinces in about two-thirds of the archipelago.

Coast guard and other disaster-response groups rescued 125 people from stricken sea vessels and flooded villages, according to Benito Ramos, who heads the government's National Disaster Risk Reduction and Management Council.

Fierce rain and winds, compounded by a high tide, swamped a boulevard in the Philippine capital with garbage-laden water from Manila Bay and forced the US Embassy to close Wednesday.

Manila schools were also closed due to sporadic flooding and strong winds.

- AP