Mayon, known for its near-perfect cone, last erupted in 2014.
The Philippine Institute of Volcanology and Seismology (Phivolcs) has raised its alert level status from 1 to level 2 as the volcano began to spew ash and steam.
There was no immediate information on whether the latest phreatic or steam-driven eruption produced a bigger ash cloud than the first two eruptions at around 5 p.m. Saturday and 8:49 a.m. Sunday, she said.
The Mayon volcano in the Philippines has spewed ash several times over the weekend, forcing authorities to evacuate two villages in its vicinity and raise the threat level, warning of potential "hazardous magmatic eruptions".
The authorities have warned people off a six-km radius around the volcano, and have issued a level 2 alert as concern grew over the possibility of stronger and more unsafe eruptions.
"Mayon's summit crater is now exhibiting [a] bright crater glow that signifies the growth of a new lava dome and beginnings of lava flow towards the southern slopes", Phivolcs added, explaining that magma is already at the volcano's crater.
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In view thereof, DOST-PHIVOLCS is raising the Alert Level of Mayon Volcano from Alert Level 1 (abnormal) to Alert Level 2 (increasing unrest).
"The public is strongly advised to be vigilant and desist from entering the 6k-radius Permanent Danger Zone to minimise risks from sudden explosions, rockfall and landslides", Phivolcs said.
"In case of ash fall events, which are most likely to affect communities on the western and southwestern flanks downwind of Mayon's crater, people should cover their nose and mouth with damp, clean cloth or dust mask", PHIVOLCS said.
People living close to the volcano, but outside the official danger zone, were told to take precautionary measures against roof collapses due to accumulated ash and rainwater. It was at its most deadly in February 1841, when 1200 people were killed and lava buried a town.
Phivolcs chief Renato Solidum said the volcano appeared due for another eruption.
"We have not reached the critical level", he said in a radio interview.