MANILA, March 22 (Xinhua) -- The Philippine authorities on Sunday raised the alert status of Bulusan volcano in Sorsogon province to Alert Level 1, signaling low-level unrest.

In an advisory, the Philippine Institute of Volcanology and Seismology said the volcano has recorded 475 volcanic earthquakes since March 15. Most of these were weak volcano-tectonic earthquakes that are associated with rock fracturing at shallow depths beneath the volcano edifice.

Bulusan volcano is located in the Bicol Region on the island of Luzon. The Philippines has 24 active volcanoes, four of which are under close monitoring. ■