The Mayon Volcano in Philippines' Albay province is "quietly erupting", authorities said on Thursday.
The Philippine Institute of Volcanology and Seismology warned of a "potential explosive activity within weeks or even days" of the country's most active volcano located on the southernmost tip of Luzon island, raising the alarm over the 2,460-meter volcano to the third level in a five-step warning system, reports Xinhua news agency.
"The overall monitoring parameters indicate that very slow extrusion of shallow degassed magma is ongoing and is incrementally increasing rate, i.e., an effusive magmatic eruption is taking place," the institute said in a bulletin.
"This means that Mayon is exhibiting magmatic eruption of a summit lava dome, with increased chances of lava flows and hazardous pyroclastic density current affecting the upper to middle slopes of the volcano and potential explosive activity within weeks or even days," it said.
The institute raised the new alarm four days after it warned on Monday the volcano's "increasing unrest" that can lead to an either phreatic or magmatic eruption.
The institute advised the evacuation of people in the 6 km radius danger zone "due to the danger of pyroclastic density current, lava flows, rockfalls, and other volcanic hazards."
"Increased vigilance against pyroclastic density currents, lahars, and sediment-laden streamflows along channels draining the edifice is also advised," it added.
The institute 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.
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