Typhoon Soudelor is set to shortly make landfall in Taiwan, with the storm forcing thousands to evacuate.
An eight-year-old girl and her mother have become the first casualties, after they were swept out to sea off Taiwan, officials said on Friday. The child's twin sister is also missing.
Troops evacuated villagers from remote mountain regions in the east of the island and helped secure their homes as rains and surging waves battered the coast.
More than 2000 people, many of them tourists, had already been evacuated from Taiwan's outlying islands.
The typhoon is set to make a direct hit on the east coast in the early hours of Saturday before moving across central Taiwan to Fujian province in mainland China.
Billed as the biggest typhoon of the year earlier in the week, Soudelor has since weakened but authorities warned it may strengthen again before making landfall.
The young girl and her mother were swept out to sea in Taiwan's eastern Yilan county on Thursday.
The dead girl's twin was also missing in the same incident, while another nine-year-old girl was injured but survived.
"The group went to the beach but were swept out to sea by strong waves," a spokesman for the fire bureau in Yilan County told AFP.
"It was a mother, her twins, and a friend's daughter. The adult and her daughter had already lost their heartbeat when brought to shore. The other child was conscious.
"The search for the missing girl stopped for today as it was getting dark but will continue."
Troops helped move residents from aboriginal villages in the eastern counties of Yilan and Hualien on Friday afternoon as well as reinforcing their houses, which will bear the brunt of the storm.