The PHIVOLCS said the escalation from alert level 1 (low-level unrest) to alert level 2 (increasing or moderate level of unrest) indicates that magma is moving beneath the volcano, increasing the likelihood of sudden explosive activity.
"This means that there is current unrest driven by shallow magmatic processes that could lead to hazardous magmatic eruption," the institute said in an advisory, Xinhua reported.
"The public is strongly advised to be vigilant and refrain from entering the six-kilometer-radius Permanent Danger Zone," added the institute, stressing that the restriction is crucial to minimizing risks from explosions and related hazards.
Mayon is the country's most active volcano and has a long history of eruptive activity.