Philippines on highest alert as super typhoon approaches

The Philippines raised its highest storm alert and evacuated thousands of people on Thursday, as Super Typhoon Usagi barrelled towards its already disaster-ravaged north.

Packing sustained winds of up to 180km an hour, Usagi is set to smash onto the main island of Luzon in the afternoon local time — the fifth storm to threaten the country in just three weeks.

The brutal wave of weather disturbances has already killed 159 people and prompted the UN to request $32.9 million in aid for the worst-affected regions.

The national weather agency said the winds could cause "almost total damage to structures of light materials, especially in highly exposed coastal areas", and "heavy damage" to buildings otherwise considered "low-risk".

"Intense to torrential rain" and potentially "life-threatening" coastal waves of up to three metres were also forecast over two days, with the storm warning raised to the highest signal on a five-step scale.

"Evacuations are ongoing" in coastal and low-lying areas of Cagayan province, its civil defence chief Rueli Rapsing told by phone.

He expects local governments to take 40,000 people to shelters, roughly the same number that were preemptively evacuated ahead of Typhoon Yinxing, which struck Cagayan's north coast earlier this month.

He said more than 5,000 Cagayan residents were still in shelters following the previous storms.

This was because the Cagayan river, the country's largest, remained swollen from heavy rain that fell in several provinces upstream, flooding communities downstream.

"We expect this situation to persist over the next few days" as Usagi brings more rain, Rapsing said.

After Usagi, Tropical Storm Man-yi is also forecast to strike the Philippines' population heartland around the capital Manila this weekend.

"Typhoons are overlapping. As soon as communities attempt to recover from the shock, the next tropical storm is already hitting them again," UN Philippines Resident and Humanitarian Coordinator Gustavo Gonzalez said.

"In this context, the response capacity gets exhausted and budgets depleted."

About 20 big storms and typhoons hit the archipelago nation or its surrounding waters each year, killing scores of people and keeping millions in enduring poverty.

A recent study showed that storms in the Asia-Pacific region are increasingly forming closer to coastlines, intensifying more rapidly and lasting longer over land due to climate change.