There were no immediate reports of casualties in the latest explosion of Mount Kanlaon, on central Negros island, but authorities shut schools and imposed a nighttime curfew after several villages were hit by ashfalls that clouded the the visibility of motorists and sparked health concerns.
"It sounded like a cannon," Mayor Jose Chubasco Cardenas of Canlaon city, which lies southeast of the volcano, told The Associated Press by telephone. "There have been quiet eruptions before, but this was one very loud."
Disaster-response officials raised the danger level around Kanlaon due to "a greater risk of hazardous volcanic activity" and ordered villagers within a six-kilometer (3.7-mile) radius of the crater to be evacuated.
About 100 people had fled to emergency shelters in Canlaon by nightfall after the mid-afternoon volcanic eruption, Cardenas said. The number of displaced people could reach more than 2,000 due to stronger prospects of more eruption, he added.
The Philippines' Institute of Volcanology and Seismology said the eruption had caused a pyroclastic density current — a superhot stream of ash, debris and rocks that can incinerate anything in its path.
The alert level around Kanlaon is at the third-highest of a five-step warning system, indicating "magmatic eruption has begun that may progress to further explosive eruptions."
The 2,435-meter (7,988-foot) volcano, one of the country's 24 most-active volcanoes, last erupted in June sending hundreds of villagers to emergency shelters.
Located in the so-called Pacific "Ring of Fire," a region prone to earthquakes and volcanic eruptions, the Philippines is also lashed by about 20 typhoons and storms a year, making one of the world's most disaster-prone.