MANILA, Jan. 14 (Xinhua) -- Philippine authorities raised its alert level of the Mayon volcano on Sunday for the second time in less than 24 hours from "increasing unrest" to "increased tendency towards eruption" within weeks or even days.

"This means that Mayon is exhibiting relatively high unrest and that magma is at the crater and that hazardous eruption is possible within weeks or even days," the Philippine Institute of Volcanology and Seismology (Phivolcs) said in its latest advisory.

The institute said there has even a continuing increase of seismic activity since the initial ash explosion on Saturday afternoon.

For the past 24 hours, Mayon Volcano in Albay Province has "noticeably increased its unrest," according to the institute.

After three phreatic or steam-driven eruptions and 158 rockfall events between 4:21 p.m. on Saturday and 7:25 p.m. on Sunday, the institute said Mayon's summit crater "is now exhibiting bright crater glow that signifies the growth of a new lava dome and beginnings of lava flow towards the southern slopes."

Already, authorities ordered the evacuation of residents within the 6-km radius permanent danger zone and a 7-km extended danger zone on the southern flank due to the danger of rockfalls, landslides and sudden explosions or dome collapse that may generate hazardous volcanic flows.

The volcano is more than 300 kilometers southeast of the Philippines capital of Manila.