Nearly 87,000 people in the Philippines have been ordered to leave their homes immediately following the strongest eruption of Mount Kanlaon in recent years.
The National Disaster Risk Reduction and Management Council on Tuesday directed everyone living within a 10km radius of the volcano to move out to safer areas.
Kanlaon on the central Negros Island is one of the 24 active volcanoes in the Philippines. It erupted for nearly four minutes on Monday, sending a massive column of volcanic ash high into the sky.
The ash fell over a wide area, as far as the Antique province, which lies over 200km across the sea from the volcano, obscuring visibility and posing health risks, Philippine chief volcanologist Teresito Bacolcol said.
Staying within a 4km radius of the volcano was prohibited as a “sudden and more explosive eruption” was still possible, he added.
The Civil Aviation Authority of the Philippines had earlier warned aircraft to avoid the volcano area until Tuesday morning due to the “possible hazards from sudden steam-driven or phreatic eruptions and precursory magmatic activity”.
The volcanic eruption caused at least six domestic and one international flight to be cancelled and two local flights to be diverted on Monday and Tuesday.
The Office of Civil Defense said that a total of 9,403 individuals, or 2,880 families, had been evacuated from five cities and towns around Mount Kanlaon.
The situation remained critical in La Castellana in the Negros Occidental province, where an estimated 46,900 people were reported to be living within the 6km danger zone.
The Philippine Institute of Volcanology and Seismology raised the alert level indicating that a “magmatic eruption” may have started and could progress to more explosive eruptions.
The institute said the alert level could be further elevated from level 3 to 5 of the five-step warning system as the situation remained volatile.
"Anytime it may progress into more explosive explosions even without signal due to its monitoring parameters like volcanic earthquakes and ash emission events," Mr Bacolcol said.
Maria Antonia Bornas, head of volcano monitoring at the institute, warned of the deadly impact of pyroclastic density currents, which are high-speed surges of hot ash, gases, and fragmented volcanic rock.
“Being hit by these pyroclastic density currents is like being run over by a high-speed vehicle,” she said.
President Ferdinand Marcos Jr said the government was ready to provide support to the displaced villagers and that his social welfare secretary had flown early Tuesday to the affected region.
"We are ready to support the families who have been evacuated outside the 6km danger zone," he told reporters.
Authorities had established evacuation centres and were seeking supplies of face masks, food and hygiene packs.
Schools were shut and a nighttime curfew imposed in the most vulnerable areas as doctors urged those in the danger zones to wear masks.
“It is a one-time but major eruption," Mr Bacolcol told the Associated Press news agency, adding that volcanologists were assessing if it was old volcanic debris and rocks clogged in and near the summit crater that was expelled or the explosion was caused by rising magma from underneath. Few volcanic earthquakes were detected ahead of the explosion, he said.
Mount Kanlaon, a 2,435m volcano, has erupted over 40 times since 1866. It last erupted in June this year, sending hundreds of villagers to emergency shelters.
Another eruption in 1996 killed at least three hikers near the peak.
Additional reporting by agencies.
