A strong typhoon skirted past most of the Philippines but appeared to be gaining strength as it headed directly for Taiwan, forecasters said.

The Philippine meteorological agency said Typhoon Chanthu was on the cusp of becoming a category 5 “super typhoon” with sustained winds of 134 mph at its centre and gusts up to 165 mph as it moved past the extreme north-eastern portion of Cagayan province.

A super typhoon is one with sustained winds of 137 mph or more.

Authorities warned that even if the eye of the storm remained off the coast, it could bring flash floods and landslides to Cagayan as well as gale to storm-force winds on shore, and cause extremely rough seas.

“Mariners are advised to remain in port or take shelter in port until winds and waves subside,” the Philippine Atmospheric, Geophysical and Astronomical Services Administration said.

Forecasts suggest the typhoon will hit the east coast of Taiwan on Sunday morning. Taiwan’s Central Weather Bureau has issued a typhoon warning as it tracks the storm.

The bureau said high waves were expected along Taiwan’s southern coast and in the Bashi Channel between its southern tip and the northernmost island in the Philippines.

A smaller typhoon slammed into the eastern Philippines on Tuesday, causing power outages in several provinces before weakening into a severe tropical storm as it moved west-northwest over the Sibuyan Sea.

About 20 typhoons and storms batter the Philippines each year, aside from seasonal monsoon rains.

The country also lies in the so-called Pacific Ring Of Fire, a region prone to earthquakes and volcanic eruptions, making it one of the world’s most disaster-prone nations.