With wind gusts of 200 kilometres an hour, authorities said they feared many people may have died as Typhoon Utor swept across coastal and mountainous regions of the northern Philippines.
"It looks like the death and damage toll is going to go up... with wind like this, you can expect a lot of damage," Francis Rodriguez, a senior officer with the National Disaster Risk Reduction and Management Council, told AFP.
Rodriguez said authorities had only started to receive reports from isolated areas that had were in the Utor's direct path early on Monday morning, and Utor was expected to continue battering the country for most of the day.
Hundreds of people die each year in the Philippines from the roughly 20 typhoons that strike the country annually.
Rodriguez said the first confirmed fatality from Utor was a man crushed by a landslide while trying to clear a mountain road in the northern Benguet province.
Twenty-three fishermen were missing after they went out to sea as the storm approached, according to the disaster council's spokesman, Reynaldo Balido.
He expressed hope the fishermen had just sought safe refuge somewhere and would still emerge alive.
Authorities said large areas of the coastal province of Aurora, where the storm made landfall, suffered heavy damage.
"Infrastructure, farms, homes were destroyed. Trees were knocked down," Elson Egargue, Aurora's disaster management officer, told AFP.
He said the coastal town of Casiguran, home to about 20,000 people, was believed to have particularly suffered, although officials had yet to make contact with residents or authorities there.
"The roads in these areas are blocked because of landslides and overflowing creeks," he said, adding mobile phone networks were also down.
He said there was also extensive damage to two other nearby towns, home to about 25,000 people.
In Manila, the nation's capital, roughly 200 kilometres to the south of the storm's path, there was heavy rain overnight but no major flooding.
Schools across the capital were closed on Monday in an automatic response to a government storm alert.
Such precautionary measures have become standard in the Philippines after the death tolls of storms in recent years have been exacerbated by poor preparations.
Over a thousand people were killed when Typhoon Bopha hit the Philippines in December, the deadliest storm in the world in 2012.
In 2009, more than 460 people were killed when tropical storm Ketsana led to flooding across 80 percent of Manila.
The weather bureau said it expected Utor would travel west out of the Philippine and into the South China Sea, towards southern China, on Monday night.
Authorities in Hong Kong said they were preparing for Utor to potentially dump heavy rains there this week. The Hong Kong Observatory raised a stage one typhoon alert. Stage 10 is its highest-level alert.