Mount Bulusan in the province of Sorsogon, Bicol, has shown signs of low-level unrest in the past 24 hours, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Tuesday.

Based on the seismic bureau's monitoring, 24 volcanic tremors occurred in the volcano, whose edifice is noted to be inflated.

It also emitted a moderate plume, reaching 100 meters, and generally drifted southwest.

On 1 April this year, it spewed 50 tons of sulfur dioxide, or SO2.

Alert Level 1 is maintained in Bulusan due to a low level of volcanic unrest with a slight increase in volcanic earthquakes and steam or gas activities.

Entry into the four-kilometer-radius permanent danger zone and entry without vigilance into the extended danger zone (EDZ) is prohibited, PHIVOLCS noted.

The flying of aircraft close to the volcano's summit is also prohibited, as ash from sudden phreatic eruptions can be hazardous to the plane.