The explosive eruption of the Bulusan volcano in the rural province of Sorsogon lasted about 17 minutes, sending a gray plume for at least a kilometer, according to the Philippine Institute of Volcanology and Seismology.
In response, the authorities raised the alert level to 1 out of 5, signaling “low intensity disturbances”.
“There was a phreatic eruption of the Bulusan volcano, which means that the explosion was caused by boiling water under the crater,” Renato Solidum, the director of the institute, told local radio DZBB.
Ash hit two towns in Sorsogon, about 500 kilometers south of the capital Manila, but no injuries were immediately reported, the institute said.
In Juban, the ashes caused “zero visibility” in two localities, and a fire truck intervened to clean the area, explained an official from the Office of Natural Disasters, Dennis Despabiladeras.
“The evacuation is underway there, and our priority is the elderly and people with asthma,” he told AFP.
The Manila airport authority said no flights had been affected so far, although pilots had been warned not to approach the area of the eruption.
Philippine authorities reminded residents of the ban on entering within a four-kilometer radius of the volcano, and advised people living nearby to be cautious “due to increased possibilities of sudden and dangerous phreatic eruptions”.
Residents near valleys and rivers were also told to be alert to mudslides in the event of heavy rain.
Bulusan Volcano has been active in recent years, with a dozen similar eruptions recorded in 2016 and 2017.
The Philippines is located in the seismically active Pacific “Ring of Fire” and has more than 20 active volcanoes.