MANILA (REUTERS) - The Philippines' most active volcano spewed lava that cascaded downslope and emitted ash that fell on nearby towns, state volcanologists said on Tuesday (Jan 16), prompting the provincial government to shut more schools.

The Philippine Institute of Volcanology and Seismology (Phivolcs) recorded nine episodes of tremor, four of which accompanied lava fountains, and 75 lava collapse events as pressure builds up leading to lava flows and ash plumes, reiterating its warning that a hazardous eruption could happen any time.

Mount Mayon, a volcano in the coconut-growing central Bicol region that draws tourists because of its near-perfect cone shape, has shown increased restiveness since Saturday, displacing thousands of residents.

Phivolcs said the advancing lava and pyroclastic flows had reached the six-kilometre radius no-go zone, from which some residents fled.

"Alert level 3 remains in effect over Mayon Volcano, which means that it is currently in a relatively high level of unrest as magma is at the crater and hazardous eruption is possible within weeks or even days," it said.

Alert level 4 means an eruption is possible "within days" while level 5 is when a hazardous eruption is under way.

The Albay provincial government has expanded its class suspension order to include more towns around the 2,462-metre volcano, and advised travellers to avoid ashfall-hit villages amid poor road visibility.

Class suspensions have allowed the government to use schools as temporary shelters for displaced people.