The typhoon, which is gaining strength as it proceeds on a collision course with southern China, was expected to make landfall over the Philippines' Babuyan Islands around midday.

The sparsely populated islands lie about 740 kilometres (460 miles) south of Taiwan, where smaller-scale evacuations were also underway.

As of 11:00 am (0300 GMT), maximum sustained winds of 215 kilometres per hour were reported at the storm's center, with gusts reaching up to 265 kph as it moved westward towards the Babuyans, the national weather service said.

"I woke up because of the strong wind. It was hitting the windows, and it sounded like a machine that was switched on," said Tirso Tugagao, a resident of Aparri, a coastal town in northern Cagayan province.

"I'm seeing from my house here that the high waves are crashing onto the shore," the 45-year-old teacher said. "I pray everyone will be safe."

Cagayan disaster chief Rueli Rapsing told AFP that his team was prepared for "the worst".

President Ferdinand Marcos said on Facebook he was closely monitoring the situation and that all government agencies were "on alert to give help anywhere and whenever needed".

In Taiwan, the state weather service predicted a chance of "extremely torrential rain" in the country's east.

"Its storm radius is quite large, about 320 (kilometres). Although the typhoon's center is still some distance away, its wide, strong wind field and outer circulation are already affecting parts of Taiwan."

James Wu, a local fire department officer, told AFP that evacuations were ongoing in mountainous areas near Pingtung.

"What worries us more is that the damage could be similar to what happened during Typhoon Koinu two years ago," he added, describing a storm that saw utility poles collapse and sheet-metal roofs sent flying into the air.

Schools and government offices were closed Monday in the Manila region and across 29 Philippine provinces in anticipation of heavy rainfall.

Government weather specialist John Grender Almario said Sunday that "severe flooding and landslides" could be expected in the northern areas of the main island Luzon.

The threat of flooding from Ragasa comes just a day after thousands of Filipinos took to the streets to protest a growing corruption scandal involving flood control projects that were shabbily constructed or never completed.

The Philippines is the first major landmass facing the Pacific cyclone belt, and the archipelago is hit by an average of 20 storms and typhoons each year, putting millions of people in disaster-prone areas in a state of constant poverty.

Scientists warn that storms are becoming more powerful as the world warms due to the effects of human-driven climate change.