The Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Thursday raised the alert level of Mayon Volcano in Albay province on Luzon island following signs of increased volcanic activity.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.