At least one person has been killed and 13 others are missing after Typhoon Utor struck the northern Philippines, triggering landslides and floods.

The national disaster agency said on Monday it was concerned for 13 missing fishermen, as more than 7,000 people have been forced from their homes.

"They went out to sea before we declared that a storm was approaching," said Reynaldo Balido, spokesman for the National Disaster Risk Reduction and Management Council.

Later on Monday, the government disaster agency reported that seven of the missing fishermen from Camarines Norte had been found.

"Some video footage shows people being swept away in raging torrents, so the death toll could rise considerably," said Al Jazeera's senior meteorologist Richard Angwin.

He added that computer forecasts suggest accumulations of 300 to 500mm of rain which would cause widespread flooding, while the hurricane force winds is estimated to have affected 21 million people.

Al Jazeera's Steff Gaulter explains Typhoon Utor

The weather bureau said Utor, packing gusts of 200km per hour, was the strongest storm of the year.

There were also concerns for remote towns and villages that had been isolated by the storm, with telecommunications networks to the areas out of order and roads cut off by landslides.

After building strength in the Pacific Ocean, Utor hit the northern regions of the main island of Luzon at 3:00am local time on Monday (19:00 GMT on Sunday).

Television footage from Aurora province, along the east coast of Luzon where Utor made landfall, showed uprooted trees that had fallen on top of houses, while roofs were ripped off some buildings.

Schools closed

The civil defence director for Aurora province, Josefina Timoteo, said reports had been received of more than 600 houses and 12 school buildings being damaged in one town, Dinalungan.

The coastal town of Casiguran in Aurora province, northeast of the capital Manila, suffered the worst damage, the provincial governor Gerardo Noveras told local media, adding that the full extent of damage was still unknown.

The typhoon, the 12th tropical cyclone this year, is expected to sweep through the northern Philippine provinces of Benguet and Ilocos Sur before exiting towards the South China Sea by Tuesday, weather and disaster officials said.

In Manila, roughly 250km to the south, there was heavy rain overnight but no major flooding. With more rain expected, many schools across the capital were closed on Monday.

Source: Al Jazeera and agencies