Typhoon Chata'an left 18 people dead or missing including five South Koreans in the Philippines over the weekend.
More than 10,000 people have been made homeless.
Chata'an, packing winds of up to 170 kilometres (105 miles) per hour, dumped torrential rain on the Southeast Asian archipelago over the weekend while en route to southern Japan.
"There is a disaster going out there," President Gloria Arroyo said in a speech before military personnel.
She ordered the air force to step up rescue efforts and "fly and extricate stranded flood victims from rooftops and places unreachable by land."
Three of the 15 recorded deaths were South Korean tourists who drowned when their boat capsized in rough waters south of Manila on Saturday, the civil defense office said.
They were going to an island resort in the central Philippines when disaster struck. Three other people, including two South Koreans from the same party, are missing and 29 were injured.
Landslides, drownings and a road accident accounted for the 12 other deaths.
Floodwaters began to ebb early today, but intermittent rain persisted into the afternoon. The chief state weather forecaster warned of more rain in provinces north of Manila.
AFP