Philippines authorities have urged some 450,000 people to flee a potential “hazardous explosive eruption” of the Taal volcano, which has been spewing ash and lava since Sunday.
Lava was sent half a mile into the sky overnight on Tuesday as Philippine Institute of Volcanology and Seismology said it supported a “total evacuation” of people within a 14km radius of the volcano.
Some 50 volcanic earthquakes have been detected in just hours, it added, and warned aircraft “to avoid the airspace around Taal volcano as airborne ash and ballistic fragments from the eruption column pose hazards”.
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Volcanic earthquakes are caused by the movement of molten rock below the surface and may be a sign of an impending eruption.
The 1991 eruption of Mount Pinatobu in the Philippines - said to be the second largest of the 20th Century - was preceded by several weeks of small earthquakes.
A level 4 alert (as now applies to Taal) was issued on 7 June 1991, followed by a level 5 alert on 13 June. The eruption on 15 June is said to have killed more than 800 people.
Volcanic earthquakes are still being registered near Taal volcano - as you can see from the Twitter feed from the Phillippine Institute of Volcanology and Seismology.
Here's the most recent, with a magnitude of 2.1 at 5.48am local time (9.48pm GMT).
Some photos of the impact of Taal volcano
More than 350 volcanic earthquakes have been recorded near Taal since Sunday, UN spokesman Stephane Dujarric has said.
Mr Solidum also warned residents from returning to high-risk villages based on perceptions that the eruption was easing.
He warned of pyroclastic flows, super-heated material from the volcano that can travel at great speed and incinerate anything in their path.
Mr Solidum said it would take time for Taal's restiveness to ease and the lives of affected villagers to return to normal but added it's difficult to predict the volcano's behavior with certainty.
"We have to make sure that people understand and, of course, government, that this is not an activity that will just be a short while," he added.
"The speed in the rise of magma is important (in determining) when the volcano will have a strong eruption and if it will slow down and freeze," said Renato Solidum, who heads the Philippine Institute of Volcanology and Seismology.
"As of now, we don't see activities slowing down and the earthquakes still continue."
More than 500 international and domestic flights were canceled or delayed after the airport in Manila was closed on Sunday, affecting about 80,000 passengers, airport manager Ed Monreal told The Associated Press.
The airport reopened on Monday after the ash fall eased.
"Hopefully the wind direction does not change. As long as the ash fall does not reach us, then we can be back to normalcy," Mr Monreal said.
More than 38,000 people have been relocated so far to over 200 evacuation centers, UN spokesman Stephane Dujarric said.
He said UN teams are visiting evacuation centers and supporting authorities, who have asked the United Nations for help getting face masks.
The alert level since the eruption began Sunday has been 4, indicating a hazardous eruption is possible in hours to days. Level 5, the highest, means such an eruption is underway.
About 50 volcanic earthquakes were detected over eight hours Tuesday, indicating rising magma, the Philippine Institute of Volcanology and Seismology said.
It also warned that heavy and prolonged ash fall was possible in nearby villages.
At least six people have been taken to a hospital in Tagaytay city in Cavite due to respiratory ailments caused by the ash, health secretary Francisco Duque III said.
The eruption has not directly caused deaths or major damage. The death of a driver in a crash on an ash-covered road was linked to slippery conditions.
President Rodrigo Duterte visited hard-hit Batangas on Tuesday, which has been declared a calamity zone for faster disbursement of emergency funds.
Accompanied by top disaster-response officials and Cabinet members, he promised the national government would help with the cleanup and reconstruction of the devastated province once the eruption ends.
Fears over bigger eruption
The continuous activity at Taal and several new fissures cracking the ground nearby means magma is likely rising and may lead to further eruptive activity, the Philippine Institute of Volcanology and Seismology said.
The volcano has been spurting fountains of red-hot lava half a mile into the sky.
The alert level since the eruption began on Sunday has been 4, indicating a hazardous eruption is possible in hours to days.
Level 5, the highest, means such an eruption is under way.
These images captured by AP photographer Aaron Favila show people's homes covered in a blanket of ash from the volcanic eruption.
Some residents refuse to leave homes and pets
While 40,000 people have been evacuated from areas surrounding the volcano, thousands more are refusing to leave or have headed back, Reuters reports.
Some residents have reportedly returned to their homes to check on their properties, possessions and animals.
Gerry Natanauan, mayor of the city of Talisay, located within the danger zone just 311 metres from the volcano, told Reuters: “I had to put Talisay under lockdown to prevent residents who were already in the evacuation centres from returning.”
Latest travel advice
The government is advising tourists visiting the Philippines follow updates on the PhiVolcs official website.
The Foreign and Commonwealth Office stated in its travel advice: "The Philippines’ authorities are currently recommending evacuation of an area within 14km radius of the Taal main crater.
"Also be aware that due to this flights in and out of Manila international airport are subject to disruption. You should consult your carrier.
"In addition, the ash cloud is over Metro Manilla and local government authorities in Manila have begun to advise staying indoors while ash is falling."
A couple didn't let the volcano get in the way of their big day as it erupted in the background of their wedding photos.
Wedding photographer Randolf Evan captured Chino and Kat Vaflor tying the knot 10 miles away from the Taal volcano as clouds of ash spewed into the air.
Here's the latest update from our Asia Editor Adam Withnall, following a news conference by experts from Phivolcs.
The volcanology institute says several warning signs are there that, while surface activity is reducing, the threat of a massive, explosive eruption is rising.
Save The Children says that an estimated 21,000 children living in the 14km danger zone identified by the Philippines government have been evacuated from their homes since Taal first started erupting on Sunday.
The charity said it was "deeply concerned" for children who have been forced to leave their homes, are missing out on school and face hunger and disease in "cramped and unsanitary" evacuation centres.
While it has no dedicated fund for the Taal evacuees, Save The Children called on people to donate to its Emergency Fund, which helps it to respond to this and other crises.
Jerome Balinton, of the Save the Children Philippines, said the children "have no idea when or even if they will be able to return to their homes".
He told The Independent in a statement: “Our humanitarian team have just visited an arena now doubling up as an evacuation centre and it was heart-breaking.
"More than 900 people are sleeping on the cold, hard surface without mats. Due to sudden evacuation, people were not able to bring blankets, hygiene essentials, mosquito nets, and supplies for babies such as diapers."
A Philippines NGO has donated 3,000 pollution masks to the affected province, according to local media reports.
Balay Mindanaw brought 25 crates full of N95-filter face masks to Batangas after hearing reports that supplies in local markets had run out.
Leonardo Bautista, a manager at the NGO, said the masks were provided in conjunction with Disaster Aid International, and made necessary by the "very wide" coverage of ashfall.
He told news outlet ABS-CBN that distribution would be done in collaboration with the Philippine armed forces.
Classes in Manila will resume tomorrow after they were suspended for two days due to the falling ash from Taal volcano.
Isko Moreno, the mayor of Manila, issued a notice in the past hour stating that classes "in all levels in all public and private schools in the nation’s capital [will] finally resume" on Wednesday.