Manila, June 5 : The Philippine Institute of Volcanology and Seismology on Monday raised the alert level over the country's most active volcano on the southernmost tip of Luzon island due to "increasing unrest" that can lead to an eruption. The institute raised the alarm for the 2,460-meter Mayon volcano in Albay province, approximately 500 km southeast of Manila, to the second level in a five-level warning system, meaning that current unrest driven by shallow magmatic processes could eventually "lead to phreatic eruptions or even precede hazardous magmatic eruption", Xinhua news agency reported. The institute recently monitored increased rockfall from the volcano's lava dome, indicating seismic growth. From April 1, the institute recorded 318 rockfall events and 26 volcanic earthquakes. The institute warned the people in the province to stay away from a 6 km radius danger zone and urged vigilance for explosions, rockfalls and landslides. It also urged civil aviation authorities to advise pilots to avoid flying close to the volcano's summit as ash from any sudden eruption can be hazardous to aircraft. Mayon, a popular tourist destination due to its cone shape, is the country's most active volcano, having erupted more than 50 times in the last 400 years. The Philippine archipelago straddles the Pacific "Ring of Fire" and is prone to earthquakes and volcanic eruptions. /IANS