Philippines' most active volcano shows signs of unrest
State volcanologists said the frequency of volcanic earthquakes has increased on Mount Mayon, signifying the possible movement of magma below the surface that could lead to ash explosions and eventually eruption.
Authorities have raised a five-step alert system from 1 to 2.
The 2,462-metre, cone-shaped volcano in the central Bicol region spewed ash and lava from July to October 2006, sending about 30,000 people fleeing from their homes.
Typhoon-triggered mudslides along Mayon's slopes buried entire villages in December 2006, killing more than 1,000 people.
Mayon has erupted about 50 times over the last few hundred years, making it the most active volcano in the country. An eruption in 1841 killed 1,200 people.