Usagi made landfall in the town of Baggao in Cagayan province at 0530 GMT with winds of 175 kilometres (109 miles) an hour, the national weather service said -- the fifth storm to strike the country in just three weeks.

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

The national weather agency had initially raised its highest storm alert, but downgraded to its second-highest as Usagi made landfall.

It said the winds could cause "considerable damage to structures of light materials", moderate damage even to structures otherwise considered "low-risk", and uproot large trees within the next 12 hours.

"Intense to torrential rain" and potentially "life-threatening" coastal waves of up to three metres (nine feet) were also forecast over two days.

President Ferdinand Marcos, visiting storm-affected areas to dole out emergency cash assistance, urged residents to comply with evacuation orders.

"We know that it is difficult to leave your homes and possessions, but sheltering could save lives," he told residents of Mindoro island south of the capital Manila, according to an official transcript of his speech.

"While we cannot prevent typhoons from hitting the country, we can take steps to reduce their impact," he said, calling for better infrastructure to cope with worsening storm effects he blamed on climate change.

- 'Forced evacuations' -

In Cagayan, officials worked in driving rain Thursday to evacuate residents along the coasts and on the banks of already swollen rivers.

"Yesterday it was preemptive evacuations. Now we're doing forced evacuations," local disaster official Edward Gaspar told AFP by phone hours before landfall, adding 1,404 residents were sheltering at a municipal gym.

"There are many more evacuees in nearby villages but we haven't had time to visit and count them," he added.

Cagayan's civil defence chief Rueli Rapsing said he expected 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.

More than 5,000 Cagayan residents were still in shelters following the previous storms because the Cagayan river, the country's largest, remained swollen from heavy rain that fell in several provinces upstream.

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

- Overlapping typhoons -

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

A high-pressure area in southern Japan will cause the storm to follow a more southerly track than Usagi, the weather service said.

"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."

A UN assessment of the past month's weather disasters said 207,000 houses had been damaged or destroyed, and nearly 700,000 people were seeking temporary shelter.

Many families were without even essentials like sleeping mats, hygiene kits, and cooking supplies, and had limited access to safe drinking water, it said.

The storms destroyed thousands of hectares of farmland and persistent flooding is likely to delay replanting efforts and worsen food supply problems, the report added.

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.