Alert level 1 has been hoisted over Mt. Kanlaon in Negros, the Philippine Institute of Volcanology and Seismology (Phivolcs) said Friday.

Phivolcs said the volcano has entered a period of unrest and "is in an abnormal condition."

Kanlaon Volcano’s seismic monitoring network recorded a total of 244 volcanic earthquakes since June 24.

The increased seismic activity could be succeeded by steam-driven or phreatic eruptions at the summit crater, despite the absence of visible degassing or steaming from the active vent this year, Philvolcs said.

Local government units and the public may not enter the 4-kilometer radius Permanent Danger Zone due to possibilities of sudden and hazardous steam-driven or phreatic eruptions, Phivolc science research specialist Jay Jamelo said.

Phivolcs also advised civil aviation authorities and pilots to avoid flying close to the volcano’s summit as ejecta from any sudden phreatic eruption can be hazardous to an aircraft.