Clouds of ash blew more than 100 kilometers (62 miles) north of the Taal volcano, reaching the bustling capital, Manila, and forcing the shutdown of the country's main airport with more than 500 flights cancelled so far.
There have been no reports of casualties or major damage from the eruption that began Sunday.
Police reported that more than 13,000 villagers have moved to evacuation centers in the hard-hit province of Batangas and nearby Cavite province, but officials expect the number to swell with hundreds of thousands more being brought out of harm's way.
The current evacuation numbers are likely higher since local authorities are busy helping displaced people before notifying the national agency that is collating the figures. Some residents could not move out of ash-blanketed villages due to a lack of transport and poor visibility immediately, while others are refusing to leave their homes and farms.
"We have a problem, our people are panicking due to the volcano because they want to save their livelihood, their pigs and herds of cows," Mayor Wilson Maralit of Balete town told DZMM radio. "We're trying to stop them from returning and warning that the volcano can explode again anytime and hit them."
Maralit, whose town lies along the shoreline of Taal Lake surrounding the erupting volcano, appealed for troops and additional police to be deployed to stop distraught residents from sneaking back to their high-risk villages.
Several planes stranded at the Manila airport may be allowed to take off Monday once they are cleaned of ash and authorities are sure an easterly shift in ash-laden wind away from the capital would not revert, airport general Ed Monreal told a news conference. The airport cannot accommodate incoming flights until stranded aircraft fly out and free up parking bays, he said.
President Rodrigo Duterte's aircraft was able to land Monday, however, after his flight from his southern Davao city hometown was delayed on Sunday by the volcanic eruption, his spokesman said.
Taal had been restive for months until it suddenly rumbled back to life Sunday, blasting steam, ash and pebbles up to 10 to 15 kilometers (6 to 9 miles) into the sky, according to the Philippine Institute of Volcanology and Seismology. The lava spurting from the volcano's vents Monday was falling into the lake surrounding the crater.
The government volcano-monitoring agency raised the danger level around Taal three notches to level 4, indicating "an imminent hazardous eruption." Level 5, the highest, means a hazardous eruption is underway and could affect a larger area with high-risk zones that would need to be cleared of people, said Renato Solidum, who heads the institute.
Ma. Antonio Bornas, the agency's chief volcanologist, said Taal spurted fountains of lava early Monday while its ash and steam ejections slightly eased. It's hard to tell when the eruption would stop, she said, citing the volcano's similar restiveness in the 1970s that lasted for about four months.
With the ashfall easing Monday morning, some residents began to shovel away inches of ash that covered everything from homes to cars and roads in Tagaytay, a popular upland resort city on a ridge that overlooks the small but picturesque volcano in the middle of a crater lake. Many of the city's restaurants and coffee shops, however, were closed, its main road covered in volcanic ash.
Large numbers of displaced villagers worried about the homes, farms and cattle they left behind and the uncertain future they face. Irene de Claro, a mother of four, worried about her father, who stayed in their village in Agoncillo town in Batangas while the rest of the family fled in panic.
"My father is missing. We don't know too what happened to our house because the ash was up to our knees, it was very dark and the ground was constantly shaking when we left," de Castro told The Associated Press in a school in Lemery town in Batangas. "Most likely there's nothing for us to return to. We're back to zero."
She later paused as the ground shook again.
The volcanology institute reminded the public that the small island where the volcano lies is a "permanent danger zone," although fishing villages have existed there for years. It stressed that the "total evacuation" of people on the volcano island and lakeshore "at high risk to pyroclastic density currents and volcanic tsunami within a 14-kilometer (8.7-mile) radius from Taal."
Authorities continue to detect swarms of earthquakes, some of them felt with rumbling sounds, and a slight inflation of portions of the 1,020-foot (311-meter) volcano, officials said and advised residents to stay indoors and wear masks and goggles outdoors.
Government work and classes in schools in a wide swath of towns and cities were suspended Monday, including in Manila, to avoid health risks posed by the ashfall. At least four Batangas towns reported power outages.
One of the world's smallest volcanoes, Taal is among two dozen active volcanoes in the Philippines, which lies along the so-called Pacific "Ring of Fire," a seismically active region that is prone to earthquakes and volcanic eruptions.
About 20 typhoons and other major storms each year also lash the Philippines, which lies between the Pacific and the South China Sea, making it one of the world's most disaster-prone countries.