Manila - A volcano in the eastern Philippines spewed ash Wednesday, prompting government volcanologists to warn of an impending eruption.

The ash explosion occurred before dawn at the Mayon Volcano in Albay province, 375 kilometres south-east of Manila, according to the Philippine Institute of Volcanology and Seismology.

"This event was recorded by the seismic network as an explosion-type earthquake, which lasted for about three minutes and was accompanied by rumbling sounds," the institute said in a bulletin.

"Incandescent rock fragments at the upper slope were observed," it said.

Several villages in the towns of Camalig, Guinobatan and Ligao at the foot of the volcano experienced ashfalls.

The institute warned that Mayon's state of unrest could lead to more eruptions of ash and possibly magma.

It urged residents around the foot of the volcano to stay out of a danger zone within a 6-kilometre radius of the mountain because of the threat of sudden explosions and rockfalls from the upper slope.

The 2,472-metre volcano has erupted about 50 times since 1616. Its most violent eruption was in 1814 when more than 1,200 people were killed and a town was buried. An eruption in 1993 killed 79 people.

Its last major eruption was in 2006, forcing more than 30,000 people to flee their homes. (dpa)