Schools and offices in the south and east of the island remained closed on Sunday and more than 200 local flights were cancelled.
“It has been strengthened since yesterday,” said the unit’s deputy director, Fong Chin-tzu. “It is expected to be a considerable threat to most areas of Taiwan, with wind, rain and waves.”
He added that the storm should move west of the Taiwan Strait on Monday.
“We must take shelter from the powerful winds and heavy rains brought by the typhoon,” Fong warned.
The Interior Ministry said authorities cautiously evacuated more than 2,800 people from seven cities in Taiwan, mostly from the mountainous Hualien County near Taitung.
The streets of Hualien were deserted Sunday morning, lashed by torrential rain under dark skies.
The armed forces mobilized soldiers and equipment, such as amphibious vehicles and inflatable boats, in parts where Haikui is expected to have the most impact.
The last major storm to hit Taiwan was Typhoon Bailu in 2019, which left one person dead.
Haikui is expected to be less severe than Saola, which caused the highest threat level in neighboring Hong Kong and southern China, before weakening on Saturday.
With information from AFP