The Civil Aviation Authority of the Philippines has warned operators to avoid flying near four active volcanoes amid recent unrest, reports Manila's GMA News.

Updated Notices to Airmen were issued for Mayon, Kanlaon, Bulusan and Taal volcanoes, setting vertical limits from the surface up to between 10,000 and 13,000 feet.

The authority urged carriers to steer clear of volcanic summits and monitor official updates. The measures follow increased activity at Mayon Volcano, where the Philippine Institute of Volcanology and Seismology raised Alert Level 3 after pyroclastic density currents were recorded.

Alert Level 3 signals high volcanic unrest driven by magmatic intrusion, with the possibility of hazardous eruption within weeks. Kanlaon Volcano is at Alert Level 2, indicating increased unrest and potential steam-driven eruptions.

Bulusan and Taal remain at Alert Level 1, denoting low unrest. PHIVOLCS said Taal could produce steam-driven or hydrothermal explosions without warning, while Bulusan's activity is shallow near the crater and entry into its permanent danger zone is prohibited.