Philippines' most active volcano spewed lava fragments on Monday that rolled about a kilometer down its slope, prompting authorities to evacuate thousands of villagers.

Children, elderly and the women were immediately evacuated from farming villages near Mayon volcano's slopes on minibuses and army trucks.

On Monday, the authorities in Philippines raised the third highest alert in a five-step scale, meaning a greater eruption is possible within weeks.

The renowned perfect cone of the volcano seemed to have been swollen, deformed with lava that had risen from the earth's core.

According to regional civil defence director Bernardo Alejandro, 8,000 of the target 50,000 people had been shifted to temporary shelters, with the operation likely to run for 3 days.

The most powerful and the deadliest of the twenty typhoons that strike the country every year occur towards the end of the year, bringing storms, landslides and floods to eastern provinces such as Albay that face the Pacific Ocean.

Magma was moving up the crater each day, though for the time being the alert level would remain at three, state volcanology agency director Renato Solidum said.

The 2,640-metre Mayon, situated 330 kms southwest of Manila, is a popular attraction for foreign tourists, but also an enduring danger for anyone getting too close.