Chief weather forecaster Nathaniel Cruz said Nuri was a powerful system that likely would gain strength as it moved across Babuyan and Calayan islands in the Luzon Strait toward Hong Kong and Guangdong in eastern China.
He said the typhoon was enhancing monsoon rains and that strong winds would continue until Thursday morning.
In the capital, Manila, officials canceled classes as heavy rains flooded streets.
The Office of Civil Defense in the northern Cordillera region said a house built on a mountain in Itogon township in Benguet province was buried by a landslide that killed three brothers -- 1, 3 and 10 years old.
Another landslide in Itogon killed a 72-year-old woman in her kitchen earlier in the day, said civil defense operations chief Alex Uy. Itogon is about 125 miles (200 kilometers) north of Manila.
In Baguio city, north of Itogon, a 21-year-old woman was rescued and revived after she was buried under the rubble of her landslide-struck house.
Public works officials said landslides and boulders were being cleared from a scenic mountain road to Baguio and from a highway to the region's main vegetable growing area.
A typhoon in June killed more than 500 people across the Philippines, along with more than 850 passengers and crew of a ferry that capsized off central Sibuyan island.
Taiwan issued a typhoon warning Tuesday for ships traveling through its southern waters. If Nuri stays on its current course, the island could be affected Thursday morning, the Central Weather Bureau said.
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