The Philippines' most active volcano spewed lava that cascaded down its slope and emitted ash that fell on nearby towns.
The volcanic activity prompted the provincial government to shut more schools.
Nine episodes were recorded by the Philippine Institute of Volcanology and Seismology (Phivolcs), four of which accompanied lava fountains, and 75 lava collapse events as pressure builds up leading to lava flows and ash plumes.
Read more: 15,000 flee as Philippines warns of volcano eruption
It warned that a hazardous eruption could happen any time.
Mount Mayon, in the central Bicol region, draws tourists because of its near-perfect cone shape. It has shown increased restiveness since Saturday, displacing thousands of residents.
Phivolcs said the advancing lava and pyroclastic flows had reached the six-kilometre radius no-go zone, from which some residents fled.
"Alert level 3 remains in effect over Mayon Volcano, which means that it is currently in a relatively high level of unrest as magma is at the crater and hazardous eruption is possible within weeks or even days," it said.
Alert level 4 means an eruption is possible "within days" while level 5 is when a hazardous eruption is under way.