Taiwan deployed more than 50,000 troops on Monday and evacuated thousands of people as Typhoon Nanmadol pummelled some of the island's most densely populated areas.
Soldiers moved in to help flood-threatened residents, a motorcyclist was reported killed, and in one remote area more than 300 villagers were trapped by landslides.
The typhoon, which left at least 16 dead in the Philippines at the weekend, made landfall near the city of Taitung on the east coast of Taiwan in the early hours of Monday, according to the Central Weather Bureau.
"This is the worst typhoon to hit Taiwan since Morakot," which left more than 700 people dead or missing in 2009, a bureau official said.
A motorcyclist was killed in north Taiwan's Chungli city, after strong winds smashed a window on the fourth floor of a building, causing shards of glass to fall to the ground level, according to Cable network Eastern Television.
An official at the Central Emergency Operation Centre could not immediately confirm the report.
The typhoon was slowly moving northwest, packing winds of up to 126 kilometres (78 miles) per hour, and was 40 kilometres north of the island's fifth-largest city Tainan as of 0600 GMT, the weather bureau said.
Across the island, authorities moved more than 8,000 people to safer places, according to the emergency centre, as the first typhoon to hit Taiwan this year bore down.
"We haven't evacuated that many people since Morakot," an official at the centre said.
The ministry of defence deployed more than 50,000 troops to assist in evacuations, some navigating flooded areas in armoured personnel carriers.
TV footage showed soldiers walking through village streets in Pingtung county in southern Taiwan, helping people from homes threatened by flooding and putting them on military trucks.
The defence ministry also said it sent two C-130 transport planes to rescue 140 tourists and servicemen marooned on the offshore island of Matsu.
More than 300 people were trapped by landslides in Wutai, a remote village in Pingtung county, the emergency centre said, adding all villagers were safe.
The typhoon brought torrential rain and some parts of Taiwan had received more than 500 millimetres since early Sunday.
The weather bureau urged the public to stay away from mountainous and low-lying areas due to the threat of flash floods and landslides.
As of Monday morning, the Soil and Water Conservation Bureau had issued landslide warnings for more than 300 areas.
The Taiwan Railway Administration suspended services on two rail lines from Taitung, the city where the typhoon had made landfall.
Businesses were closed in seven cities and counties in the south of Taiwan, and in all but two of the island's counties, classes were also cancelled at all schools.
Electricity was cut to more than 20,000 households, according to the emergency centre.
Attention was also turned towards China, with the typhoon expected to gradually grind its way towards the Taiwan Straits during the course of Monday.
Southeast China's Fujian province called more than 25,000 fishing boats to port on Sunday, amid warnings that moderate to heavy downpours would hit coastal areas from Monday morning, the official Xinhua news agency reported.