He said Mayon remains "in a mild state of eruption" at present, but there were signs of a more violent eruption in the coming days or weeks.

"We have to make sure that everything is prepared. Evacuation could come in very, very quickly," he said, adding that at least 20,000 people living under its shadow could be in direct danger of lava flow

For the past 24 hours, the 2,462-meter (8,077 foot) Mayon has oozed lava and spewed out huge rocks, the Philippine Instituate of Volcanology and Seismology said in its latest bulletin.

"The advancing lava flow has now reached 1,000 meters downslope of the summit crater," it said, adding that rolling incandescent boulders could also be observed at its southeast gully.

Level three of a five-step alert system remains hoisted on Mayon, meaning that laval flow could suddenly shift to "explosive eruption which could generate pyroclastic flows" within weeks or days.

Residents, it said, should be vigilant and prepared to evacuate as soon as necessary.

Mayon, 300 kilometers (176 miles) southeast of Manila, last had a major eruption in July 2001. More than 1,000 people are believed to have perished when the volcano erupted in 1814.

Sicilys Mount Etna Rumbles Back To Life

Sicily's Mount Etna has begun spewing lava and ash and emitting rumblings that by Tuesday could be heard at 10-second intervals, Italy's ANSA news agency reported. Two streams of lava have for several days been flowing from a new crack that opened up on Friday around 3,100 metres (10,000 feet) up the eastern slope of the volcano.

Experts from the national geophysics institute who flew over the volcano in a helicopter on Tuesday also recorded an increase in the quantity of ash and lapilli, the small porous stones ejected by erupting volcanoes.

But ANSA said the latest activity posed no threat to people because the area around it is uninhabited.

Etna last erupted on June 22, 2001, throwing molten rock 400 metres into the sky and spewing lava down its sides.

It has the longest history of documented eruptions of any volcano, dating back about 3,500 years.

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