Super Typhoon Fung-wong has slammed ashore in the north-eastern coast of the Philippines, officials say, with the massive storm leaving four people dead and forcing more than a million people to evacuate from flood and landslide-prone areas.

The typhoon blew into Dinalungan town in the Aurora province on Sunday night after setting off fierce rain and wind in north-eastern Philippine provinces all day from offshore. "We could not sleep because of the winds hitting our metal sheets and tree branches falling," said Romeo Mariano, who sheltered with his grandmother in their home in the province of Isabela.

"When we got out to check our home, we saw the damage." Early indications suggest the tally of dead "will be minimal," however, civil defence senior official Raffy Alejandro told a media briefing.

Two children died after a mudslide buried a house in the northern town of Kayapa in the province of Nueva Vizcaya, regional civil defence official Alvin Ayson said by telephone. Sustained winds of 185 kilometres per hour and gusts of up to 230 kilometres per hour have been battering parts of the country, authorities said.

The biggest typhoon to threaten the Philippines in years, Fung-wong could cover two-thirds of the archipelago with its 1,800-kilometre-wide rain and wind band, forecasters said. It approached from the Pacific while the Philippines was still dealing with the devastation wrought by Typhoon Kalmaegi, which left at least 224 people dead in central provinces on Tuesday before pummelling Vietnam, where at least five were killed.

A villager drowned in flash floods in the eastern province of Catanduanes and another died in Catbalogan city in eastern Samar province when she was pinned by debris, officials said. Philippine President Ferdinand Marcos Jr has declared a state of emergency due to the extensive devastation caused by Kalmaegi and the expected damage from Fung-wong, which is also called Uwan in the Philippines.

Tropical cyclones with sustained winds of 185 kilometres per hour or higher are categorised in the Philippines as a super typhoon, a designation adopted years ago to underscore the urgency tied to more extreme weather disturbances. Roberto Monterola, a disaster-mitigation officer for Catanduanes, said the rain and wind were so strong there was almost zero visibility.

Despite calls for residents to evacuate on Saturday, some still stayed on. "Our personnel rescued 14 people who were trapped on the roof of a house engulfed in flood in a low-lying neighbourhood," Mr Monterola said.

"A father also called in panic, saying the roof of his house was about to be ripped off by the wind. We saved him and four relatives."

More than a million people were moved away from high-risk villages in north-eastern provinces, including in Bicol, a coastal region vulnerable to Pacific cyclones and mudflows from Mayon, one of the country's most active volcanoes. Defence Secretary Gilberto Teodoro Jr warned about the potentially catastrophic impact of Fung-wong in televised remarks on Saturday.

He said the storm could affect a vast expanse of the country, including Cebu, the central province hit hardest by the previous typhoon, and metropolitan Manila, the densely populated capital region. More than 30 million people could be exposed to hazards posed by Fung-wong, the Office of Civil Defence said.

Mr Teodoro asked people to follow government orders and seek shelter away from villages and towns prone to flash floods, landslides and coastal tidal surges. "We need to do this because when it's already raining or the typhoon has hit and flooding has started, it's hard to rescue people," he said.