Authorities over the weekend urged at least 50,000 people to leave their homes on the slopes of Mt. Mayon, located some 550 kilometers southeast of Manila, and some 60 percent of them had done so as of Wednesday, they said.

Molten lava continues to flow out of the crater of Mt. Mayon, one of the Philippines' most active volcanoes, while the volcano has also manifested dozens of earthquakes and tremors.

"If trend is one of increasing unrest, hazardous volcanic eruption is possible within weeks," said an advisory issued by the Philippine Institute of Volcanology and Seismology.

The alert level around the 2,474-meter volcano was raised from 2 to 3 on Monday, meaning that magma is close to the crater and sudden explosions could generate hazardous volcanic flows.

The institute currently recommends that a 6-km radius Permanent Danger Zone around the volcano and a 7-km Extended Danger Zone on the southeast flank of the volcano should be free from human activity.

Mt. Mayon, famous for its beauty and near-perfect symmetry, last erupted in 2006. Its most violent eruption was in 1814, when more than 1,200 people were killed and three towns were buried under mud and rocks.