Manila, April 13 -- Residents around Kanlaon Volcano are advised to be vigilant due to increased seismicity and long-duration tremors observed over the past 24 hours, the head of the Philippine Institute of Volcanology and Seismology (Phivolcs) said Monday.

At least 150 volcanic earthquakes, including four volcanic tremors with 40 to 100 minutes duration, were recorded.

"This may be considered an increase in seismicity at Kanlaon. The number of earthquakes, including several long-duration tremors, show that the volcano remains active internally," Phivolcs Director Teresito Bacolcol told the Philippine News Agency in an interview.

These show that the volcano "is not quiet", and the residents around Kanlaon Volcano should remain vigilant...