Air pollution blanketed Chiang Mai, northern Thailand, this week making it the third most polluted city in the world.
Aerial footage shows the smog covering the city and mountainsides on Wednesday morning (March 3).
Officials said that forest fires and agricultural burning had increased the levels of harmful PM 2.5 particles in the air.
The AirVisual website ranked Chiang Mai the third most polluted city in the world after Lahor in Pakistan and New Delhi in India.
Major General Thanadpol Kosaisewee, deputy chief of a command tackling air pollution in the region, said 928 critical areas had been detected across the region.
Smoke from mountain widfires had blanketed the city. Cooler temperatures and a lack of wind and rain had meant that it had lingered in the atmosphere.