A volcano in the Bicol Region spewed dark smoke as a phreatic eruption occurred Sunday morning, prompting state volcanologists to raise Alert Level One.

''Alert Level 1 status is now raised over Bulusan Volcano, which means that it is currently in an abnormal condition. Local government units and the public are reminded that entry into the four-kilometer radius Permanent Danger Zone must be strictly prohibited,'' said the Philippine Institute of Volcanology and Seismology (Phivolcs) in its 11:40 am report.

''Vigilance in the 2-kilometer Extended Danger Zone (EDZ) on the southeast sector must be exercised due to the increased possibilities of sudden and hazardous phreatic eruptions,'' it added.

Renato Solidum, Phivolcs director, said the phreatic explosion at Bulusan Volcano in Sorsogon took place at 10:37 am.

''It lasted for 16 minutes,'' he told dzBB. Seventy-seven volcanic earthquakes were recorded before the phreatic explosion took place, Solidum said.

Phivolcs said the eruption was ''poorly visible through cloud cover over the edifice although a steam-rich grey plume at least 1 kilometer tall was observed from Juban, Sorsogon and was subsequently observed to drift west.''

''Ashfall has been reported in Juban and Casiguran, Sorsogon,'' it added.

Pierre Dellosa, assistant department head of the Sorsogon provincial risk reduction and management office, said those barangays affected by the explosion are advised to evacuate.''

Fritzie Michaellena of the Irosin, Sorsogon municipal risk reduction and management office, said four barangays with around 800 families were affected by the explosion. She added that minimal ashfall were reported in the four barangays. DMS