The Philippines' most active volcano began spewing lava and sulfuric gas Sunday night. More than 14,000 people had been evacuated, authorities said.

Philippine Institute of Volcanology and Seismology Director Teresito Bacolcol said the Mayon volcano had an "effusive eruption" shortly before 8 p.m. local time on Sunday night.

"Lava is being poured out from the vent. It's slow-moving. It can be observed as rivers of molten lava," Bacolcol told a television interview, adding effusive eruptions are generally less violent and will produce less ash and volcano gases than explosive eruptions.

The volcano had been raised to alert level three on a five-step warning system Thursday, meaning the volcano was in a state of high unrest and a hazardous eruption is possible in weeks or days.

From Sunday, the institute has recorded 21 volcanic earthquakes, 260 rockfall events, and three fast-moving pyroclastic flows of a mixture of rock fragments, gas, and ash.

The National Disaster Risk Reduction and Management Council said over 14,000 villagers within the danger zone of the volcano have been evacuated and sheltered in school buildings and other temporary shelters. On Monday, Albay Governor Edcel Greco Lagman extended the danger zone from six to seven kilometers.

Mayon is one of 24 active volcanoes in the Philippines. It last erupted violently in 2018, displacing tens of thousands of villagers. In 1814, Mayon's eruption buried entire villages and reportedly left more than 1,000 people dead.

The archipelago is lashed by about 20 typhoons and tropical storms a year and is located on the so-called Pacific "Ring of Fire," the rim of seismic faults where most of the world's earthquakes and volcanic eruptions occur.

(With input from agencies)

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