MANILA, Jan. 22 (Xinhua) -- The Philippine authorities raised the alert level for the Mayon volcano from level three to level four on Monday, meaning that a "hazardous eruption is imminent."

Under alert level four, the Philippine Institute of Volcanology and Seismology (Phivolcs) said the Mayon volcano is experiencing "intense unrest."

Phivolcs upgraded the volcano to alert level four just a few minutes after the volcano suddenly erupted lava around noon.

In the morning report on Monday, the Phivolcs indicated that 500-meter to 200-meter high lava fountains were generated at 10:45 p.m. local time on Sunday and 2:25 a.m.local time on Monday respectively.

Mountain Mayon, one of the Philippine most active volcanos famous for its beauty and near-perfect symmetry, is in Albay province on the Philippine main Luzon Island more than 300 km southeast of the Philippines capital Manila. It has an elevation of 2,462 meters.

According to Albay Governor Al Francis Bichara, all schools will be suspended in the whole province on Jan. 23.