The crater of a rumbling Philippine volcano was glowing bright red Monday, with vulcanologists warning it could erupt within days, sending thousands fleeing from their homes.

Volcanic earthquakes and rockfalls have shaken the summit of Mayon over the last 24 hours, after a number of steam-driven eruptions, scientists said.

More than 12,000 people have been ordered to leave a seven-kilometre (four-mile) evacuation zone, and there are warnings of destructive mudflows and toxic clouds.

"It is dangerous for families to stay in that radius and inhale ash," Claudio Yucot, head of the region's office of civil defence, told AFP.

"Because of continuous rains in past weeks, debris deposited in the slopes of Mayon could lead to lahar flows. If rain does not stop it could be hazardous."