Typhoon Rai blew away Friday night into the South China Sea after rampaging through southern and central island provinces, where more than 300,000 people in its path were evacuated to safety in advance in a pre-emptive move officials say may have saved a lot of lives.

At its strongest, Rai packed sustained winds of 195km/h and gusts of up to 270km/h, one of the most powerful in recent years to hit the disaster-prone Southeast Asian archipelago, which lies between the Pacific Ocean and the South China Sea.

The typhoon slammed into the country's southeastern coast on Thursday but the extent of casualties and destruction remained unclear two days after with entire provinces still without power and mobile phone connection.

The government's main disaster-response agency said at least 31 people were reported killed, many after being hit by falling trees, but it added it was validating most of the deaths. At least three were injured and one was missing.

Officials on Dinagat Islands, one of the first provinces to be lashed by the typhoon's ferocious winds, remained cut off Saturday due to downed power and communication lines.

But its governor, Arlene Bag-ao, managed to post a statement on the province's website to say that the province of about 180,000 "has been levelled to the ground".

She pleaded for food, water, temporary shelters, fuel, hygiene kits and medical supplies. She said only a few casualties have been reported in the capital so far because other towns remain isolated.

Pictures posted on social media show low-slung houses with roofs either blown off or damaged and surrounded by tin roof sheets and debris. The island of Siargao, known as the surfing capital of the Philippines, was also pummelled by the typhoon.

In central Bohol province, which was directly hit by the typhoon, the coast guard said its personnel on board rubber boats rescued residents who were trapped on roofs and trees, as waters rose rapidly.

It released footage showing coast guard staff helping people from the roof of a house nearly engulfed by brownish floodwater to a rubber boat. They also help a villager climb down from a tree above the floodwater while another man, also wearing an orange life vest, waits for his turn.

With government contingency funds used for the coronavirus pandemic, President Rodrigo Duterte said he would look for money to help the provinces. He planned to visit the devastated region this weekend.

About 20 storms and typhoons batter the Philippines each year. The archipelago is located in the seismically active Pacific "Ring of Fire" region, making it one of the world's most disaster-prone countries.

Australian Associated Press