The most active volcano in the Philippines is expected to have a "hazardous explosive eruption" within days, a government-run institute said Sunday, raising the public alert level and recommending the cordoned-off zone to be extended.

The Philippine Institute of Volcanology and Seismology ( Phivolcs) raised the alert status of Mayon volcano, which is located in eastern Albay province or about 360 km southeast of Manila, to one step below the major eruption level after a series of increased volcanic activities were recorded over the past week.

Local government started to evacuate more than 40,000 residents living in the area earlier last week and the governor has imposed a round-the-clock entry ban to the "dangerous zone" in a radius of eight km around the volcano.

Phivolcs Bicol-based monitoring head Julio Sabit told local television network GMA News that the institute had monitored at least 463 quakes from 05:00 a.m. to 02:00 p.m. on Sunday and rumbling sounds could be heard in a nearby village.

The volcano has begun to spew lava and ashes since Dec. 14. Orange crater glow has been observed for days.

The Phivolcs said the advancing lava flow now has reached approximately 4.5 km down the slope from the crater and over the last 24 hours, sulfur dioxide emission increased more than double to 7,024 tons per day.

The perfect cone-shaped volcano, a tourist spot, has erupted 48 times, killings at least thousands. Its latest eruption was in 2006 but no one was killed.