A volcanic smog alert was raised as Taal Volcano spewed sulfur dioxide anew in the Philippines.

State seismological agency PHIVOLCS issued the warning as the haze covered 10 towns in Batangas province on March 12.

PHIVOLCS said the volcano had emitted 6,837 tonnes of sulfur dioxide on March 11. It is still under Alert Level 1, with possible volcanic earthquakes, steam-driven explosions, and minor ashfall occurring.

Volcanic smog or 'vog' is formed when acidic sulfur dioxide reacts with oxygen and moisture in the air. It can cause irritation to the eyes, nose, and respiratory tract if inhaled.

The Philippines is an archipelago of more than 7,000 islands inside the Pacific 'Ring of Fire' where the majority of Earth's volcano eruptions and earthquakes happen.