Almost half a million people fled coastal villages in Vietnam and the Philippines on Friday as two separate typhoons roared towards the southeast Asian countries.

Typhoon Mitag, with sustained winds of 175 kilometres per hour, is expected to make landfall on the small Philippines island province of Catanduanes on Saturday, the same day Typhoon Hagibis is supposed to strike the Vietnamese coast.

Mitag could intensify to a Category 3 storm before making landfall, which could bring waves of up to seven metres and dangerous storm surges, CBC News meteorologist Nick Czernkovich said.

Philippine disaster officials said more than 194,000 people have fled or been evacuated to temporary shelters in provinces on the southern tip of the main Philippine island of Luzon.

In Vietnam, officials began evacuating 200,000 people as Hagibis headed for the country after leaving 13 people dead in the Philippines earlier this week. If it makes landfall, Hagibis would be the seventh major storm to hit the country this season.

But the storm changed track late Friday and is expected to weaken overnight into a tropical storm and make landfall Saturday as a low pressure system, Czernkovich said.

"That is actually a lot of good news there, as the damage will be quite a bit less," he said.

25 sailors missing

Meanwhile, in the South China Sea, which separates Vietnam, the Philippines and China, a search was underway for 25 Filipino sailors who were missing after their fishing boat capsized in rough seas, a Chinese maritime official said.

Thirty other crew members were rescued and search teams were dispatched to look for the missing, said a man at the China Maritime Search and Rescue Centre who gave only his surname, Zhang.

Philippine President Gloria Macapagal Arroyo ordered mass evacuations along the typhoon's expected path. She cut short her visit to Singapore, where she was attending an Asian summit.

Forecasters said Mitag could veer slightly southwest and hit Albay province, which bore the brunt of last year's Typhoon Durian. The storm triggered flash floods and unleashed tons of debris, killing more than 1,000 people.