Torrential rain has turned streets into rivers, submerged entire villages and buried some vehicles in volcanic sediment set loose by the downpour.

At least 32,000 people have fled their homes in the northern Philippines, police said, as the storm edges closer to the Southeast Asian country's main island of Luzon.

In the Bicol region, about 400 kilometres (249 miles) southeast of the capital Manila, "unexpectedly high" flooding was complicating rescue efforts, said police.

"We sent police rescue teams but they struggled to enter some areas because the flooding was high and the current was so strong," regional police spokeswoman Luisa Calubaquib told AFP.

Eleven people drowned in floodwaters in the Bicol city of Naga, local police chief Erwin Rebellion told AFP.

An elderly woman drowned in Quezon province southeast of the capital, while a toddler was also killed after falling into a flooded canal, police said.

Manila's civil defence office reported one person was killed by a falling tree branch.

As of 8 pm (1200 GMT), the storm's centre was 150 kilometres east of Luzon's Isabela province with maximum sustained winds rising to 95 kilometres per hour, the national weather agency said.

It was expected to smash into the coast of Isabela sometime during the night or early Thursday, slightly weakening as it crosses the island and heads out into the South China Sea, the agency added.

More than 500 millimetres (1.64 feet) of rain, or over a month's worth, has already fallen on the region in the past 24 hours.

Photos verified by AFP on Wednesday showed streets submerged by muddy floodwaters in Camarines Sur province's Bato municipality, with only the roofs of houses and convenience stores visible.

"It's getting dangerous. We're waiting for rescuers," resident Karen Tabagan told AFP.

- 'Feeling a little helpless' -

In Naga, about 40 kilometres from Bato, half of the 600 villages were fully submerged by flooding.

At an emergency meeting of government agencies Wednesday morning, President Ferdinand Marcos said that "the worst is yet to come".

"I'm feeling a little helpless here because... all we can do is sit tight, wait, hope and pray that there is not too much damage, that there are no casualties."

Families driven from their homes in Bicol were being sheltered at about 2,500 various evacuation centres.

Volcanic sediment was also unleashed by the rain from the Philippines' famous Mayon volcano, according to Calubaquib, the Bicol police spokeswoman.

Further north in Isabela province, authorities evacuated 216 people from the coast near Divilacan and another 60 from nearby Palanan municipality after the weather service warned of "moderate to significant risk of life-threatening storm surge" or high coastal waves.

"They had to conduct pre-emptive evacuations in response to the storm surge warning ... They had to evacuate some Indigenous people who are living in houses made of light materials," Isabela provincial disaster official Constante Foronda told AFP.

Storms and typhoons are common around the region at this time of year.

However, a recent study showed that they are increasingly forming closer to coastlines, intensifying more rapidly and lasting longer over land due to climate change.

About 20 big storms and typhoons hit the Philippines or its surrounding waters each year, damaging homes and infrastructure and killing dozens of people.