Typhoon Rammasun was set to strike the Bicol region in the east of the country at 6:00 pm (local time), with Manila and other heavily populated areas also expected to be hit early tomorrow, the state weather service said.
"We are preparing for the worst... It is critical now that we finish the evacuations," said Rafaelito Alejandro, civil defence chief of Bicol, an impoverished farming and fishing region of 5.4 million people.
"If we can finish the evacuation, then it's just a waiting game to see what happens," Alejandro told AFP by telephone.
The Philippines is hit by about 20 major storms a year, many of them deadly. The Southeast Asian archipelago is often the first major landmass to be hit after the storms build above the warm Pacific Ocean waters.
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In November last year, Super Typhoon Haiyan brought the strongest winds ever recorded on land to the central Philippines, killing up to 7,300 people in one of the nation's worst ever natural disasters.
The state weather service upgraded Rammasun overnight yesterday from a tropical storm into a typhoon as its wind speeds built over the Pacific.
Rammasun, which is Thai for "God of Thunder", is expected to have gusts of up to 180 kilometres an hour when it makes landfall, according to the US military's Joint Typhoon Warning Centre.
Its eye was about 190 kilometres southeast of Legazpi, Bicol's largest city, at 9:00 am (local time), the Philippine weather service said.