Mount Mayon has been spewing lava and ash for more than a week
Scientists in the Philippines have raised the alert level for the volatile volcano Mount Mayon, amid fears of an imminent eruption.
It is now at four out of a possible five, meaning a hazardous eruption "is possible within days". Level five is when a major eruption has begun.
Scientists raised the level after the number of volcanic earthquakes more than doubled on Sunday.
The cone-shaped volcano has already been emitting lava and ash for days.
About 40,000 people who live near Mount Mayon have been moved to temporary shelters.
Scientists detected 453 volcanic earthquakes in a five-hour span on Sunday, compared to just over 200 Saturday, said Renato Solidum, chief of the Philippine Institute of Volcanology and Seismology.
Powerful booms emanating from the volcano, audible up to 12 km (7.5 miles) away, and continued lava flows all contributed to the raised alert level.
But despite the risks, local authorities estimate that roughly 1,300 families are still in their homes within the danger zone, unwilling to leave their farms and livestock.
"We will personally remove the residents who refuse to evacuate to their designated evacuation centres," said Albay provincial governor Joey Salceda.
About 8,600 families, or 43,000 people, have already taken shelter in government centres beyond the zone.
Officials said they were strengthening the army and police enforcement of an exclusion zone at least eight km (4.3 miles) around the volcano.
Philippine officials first raised the alert level for Mayon last Monday.
Mr Solidum said the pattern of volcanic activity was similar to Mayon's last eruption in 2006, when it expelled lava and steam for two months.
Mayon, 330km (206 miles) south-east of the capital Manila, has erupted 48 times since records began.
The most violent eruption, in 1814, killed more than 1,200 people and devastated several towns.
However the volcano remains a popular tourist attraction and is famous for its perfect cone.