Lava and broad columns of ash illuminated by lightning spewed from a volcano south of the Philippine capital on Monday, grounding hundreds of flights as authorities warned of a possible "explosive eruption".
Fine grit weighed down trees and turned roads into muddy messes across the region surrounding the Taal volcano, which burst to life Sunday and has forced over 20,000 people to seek refuge in evacuation centres, a provincial governor said.
Geologists said the volcano remained active, spurting red-hot lava some 500 metres (1,600 feet) into the air from new cracks that have opened in its northern flank, as accompanying earthquakes rattled the area.
"We are really scared of what might happen to us... that our house might collapse in a strong earthquake and that we'll all be killed by falling debris," said Bienvenido Musa, aged 56.
"Who wouldn't be scared? That's why I decided to send my family to an evacuation centre."
Taal is a tourist attraction that sits in a picturesque lake, yet is also one of the most active volcanoes in a nation where earthquakes and eruptions are a frightening and destructive part of life.
The Philippines sits on the Pacific "Ring of Fire", where tectonic plates collide deep below the Earth's surface.
Schools in the region around Taal, some government offices in Manila and the Philippine Stock Exchange were closed as authorities issued warnings against breathing the ash.
Stores quickly sold out of dust masks, which health officials said could help protect against potentially harmful effects of the powder-like soot.
"I'll just stay at home and tie a handkerchief around my face. I think that's OK," Manila resident Menchie Claveria said, after attempting to buy a mask.
Limited flight operations resumed mid-Monday at Manila's main international airport, nearly a day after authorities halted them due to the safety risk volcanic ash poses to planes.
However, travellers booked on over 240 cancelled flights still faced delays at Ninoy Aquino International Airport.
"I'm disappointed because this (delay) means additional expense for me and it's tiring to wait," said stranded traveller Joan Diocaras, a 28-year-old Filipino who works in Taiwan.
"But there's nothing we can do."
- Alert level raised -
The eruption began with an explosion of superheated steam and rock, but by early Monday "fountains" of lava had been spotted on Taal, the Philippine Institute of Volcanology and Seismology (Phivolcs) said.
Stunning lightning shows have periodically played out above the volcano in a little-understood phenomenon that has been attributed to static electricity.
Authorities raised the volcano alert level to its second-highest on Sunday, saying an "explosive eruption" could happen in "hours to days".
Phivolcs chief Renato Solidum told AFP the lava was evidence of fresh movement in the volcano, but said it was unclear if Taal would "sustain its activity".
Apart from the ash, some particles up to 6.4 centimetres (2.5 inches) in diameter, larger than a golf ball, had reportedly fallen in areas around the lake, Phivolcs said.
Taal's last eruption was in 1977, Solidum said.
Two years ago, Mount Mayon displaced tens of thousands of people after spewing millions of tonnes of ash, rocks and lava in the central Bicol region.
The most powerful explosion in recent years was the 1991 eruption of Mount Pinatubo, about 100 kilometres northwest of Manila, which killed more than 800 people.