The Philippine Institute of Volcanology and Seismology has recorded at least one volcanic earthquake in the past 24 hours and red-hot rocks have been falling from the crater.

The Health Secretary has warned of health risks from inhaling sulphur dioxide gas or particulate matter of ashfalls.

The Philippine civil defence office said that over 12,800 people have been moved to evacuation centres, mostly from farming villages at the foot of the volcano.

The alert system for the volcano was raised from two to three on Thursday.

Five years ago, Mayon displaced tens of thousands of people after spewing millions of tonnes of ash, rocks and lava.

The country's most powerful eruption in recent decades was Mount Pinatubo in 1991 that killed more than 800 people.