Manila, Jan 15 (IANS): The Philippines on Monday raised the alert level to critical over the possibility of a hazardous eruption of the Mayon volcano after it spewed clouds of ashes over the weekend, leading to evacuation of more than a thousand people.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) had issued the alert level 2 (growing concern) on Sunday before raising it to level 3, considering that a magmatic eruption from the valcono, in the east of the country, was imminent, Efe news agency reported.

The volcano, located around 350 km to the southeast of Manila, "is exhibiting relatively high unrest and that magma is at the crater and that hazardous eruption is possible within weeks or even days", PHIVOLCS said in a statement.

The agency said Mayon's summit crater was exhibiting "bright crater glow" that signified the growth of a new lava dome and beginnings of lava flow towards the southern slopes.

More than 900 families have been evacuated from the vicinity of the Mayon since it first erupted on Saturday afternoon.

Another two eruptions followed on Sunday, unleashing grey clouds and ashes, leading to a total of 158 rockfalls, according to PHIVOLCS.

The authorities have warned people off a six-km radius around the volcano, and have restricted air travel in the vicinity.

The biggest eruption in the history of the Philippines was that of Mount Pinatubo in June 1991, which left around 850 people dead and affected over a million.

The Philippine archipelago is situated on the so-called Ring of Fire, an area of great seismic and volcanic activity around the Pacific Ocean, and has 23 active volcanoes.