Glowing lava rolls down Philippine volcano

There are warnings that an explosive eruption is imminent as lava spills down the sides of Mount Mayon in the Philippines.

Lava is spilling Mayon Volcano in the Philippines with an explosive eruption imminent. (AAP)

Glowing red lava is rolling down the slopes of a Philippine volcano as authorities maintained a warning of a possible hazardous eruption.

The lava was quietly flowing in some places but at times Mount Mayon was erupting like a fountain, the Philippine Institute of Volcanology and Seismology said.

Lava had advanced up to two kilometres from the crater, and ash reached up to two kilometres and fell on nearby communities.

Lava cascades down the slopes of Mayon volcano. Source: AAP

Nearly 15,000 people have fled the danger zone within six to seven kilometres of Mayon, and the institute strongly advised people not to re-enter the area.

After steam explosions Saturday and lava rising in the crater on Sunday, the alert was raised to three on a scale of five, indicating a hazardous eruption is possible "within weeks or even days."

A view of rumbling Mayon Volcano as it spews ash. Source: AAP

Mayon lies in coconut-growing Albay province about 340 kilometres southeast of Manila. With its near-perfect cone, Mayon is popular with climbers and tourists but has erupted about 50 times in the last 500 years, sometimes violently.

In 2013, an ash eruption killed five climbers who had ventured near the summit despite warnings. Mayon's first recorded eruption was in 1616 and the most destructive in 1814 killed 1,200 people and buried the town of Cagsawa in volcanic mud.

Lava continues to cascade down the slopes of Mayon volcano. Source: AAP

The Philippines lies in the so-called "Ring of Fire," a line of seismic faults surrounding the Pacific Ocean where earthquakes and volcanic activity are common.

In 1991, Mount Pinatubo in the northern Philippines exploded in one of the biggest volcanic eruptions of the 20th century, killing about 800 people.