Thousands of people fled as powerful Typhoon Koppu hit the northern Philippines early Sunday, officials said, battering coastal towns with powerful winds that forecasters warned could last up to three days.

No casualties have been reported but about 6,500 people were evacuated from their homes and taken to safer ground, and the number was expected to rise as the storm slowly grinds inland across the main island of Luzon, the civil defence office said.

Koppu pounded the remote coastal town of Casiguran with gusts up to 210 kilometres (130 miles) an hour and heavy rain, remaining nearly stationary hours after making landfall there before dawn, the state weather service said.

"It looks likely this deluge will be with us for days," weather forecaster Gladys Saludes told AFP, adding the typhoon was not likely to leave Luzon until Tuesday.

Koppu downed trees and pylons, leaving two cities and 22 towns without power, while landslides and floods cut off 10 roads and eight bridges across the region, National Disaster Risk Reduction Council chief Alexander Pama told reporters.

He said ferry services across the island, home to about half the Asian archipelago's population of 100 million people, were suspended amid rough seas while commercial aviation was also disrupted with 30 flights suspended, two of them on international routes.

ABS-CBN network aired footage of strong winds shaking large trees and rattling rooftops and storefront signage in Baler, a tourist resort about 85 kilometres south of Casiguran.

- 'This is just the start' -

Pama said communications links had also been cut in many of the affected areas, while the authorities were working to evacuate more people deemed at risk and trying to clear blocked roads so aid could get through.

"I must emphasise that this is just the start. People must remain alert while we try to pick up the pieces in areas already hit," Pama added.

Residents of communities in the typhoon's expected path were hunkering down under darkening skies, said Kate Marshall, part of an advance reconnaissance team of the International Committee of the Red Cross to the region.

"There is a bit of debris around but nothing major as yet. The trees are beginning to sway a lot more," " Marshall told AFP from Solano town, about 100 kilometres inland.

"We have seen people checking roofs and putting stuff away. There are not that many people on the road.... I would say people are prepared," she said, adding local officials have prepared evacuation centres in case they are needed.

Saludes, the weather forecaster, said that due to Koppu's unusually slow pace, the mountainous areas and farmlands along river valleys in the area were expected to be pummelled by intense rain for days.

This could leave them exposed to floods and landslides, among other hazards, she said.

The weather service has also warned of storm surges, massive typhoon-generated waves smashing along coastal areas, but Saludes said there had been no reports of these so far.

Although the storm will not directly hit the capital, Manila, the weather service said it would affect a 600-kilometre swathe so that other regions were likely to be affected by strong winds and rain.

The Philippines is hit by an average of 20 storms each year, many of them deadly.

The deadliest and strongest on record, Super Typhoon Haiyan, destroyed entire towns in the central islands in November 2013, leaving more than 7,350 people dead or missing.