Around 1,670 firefighters have been deployed to tackle hotspots caused by agricultural burning in northern Thailand.

Authorities dispatched the firefighters to high-risk areas across Chiang Mai province on March 29 after the Geo-Informatics and Space Technology Development Agency (GISTDA) detected some 343 hotspot fires in the region.

The emergency services were tasked with keeping the fires at bay as helicopters failed to extinguish them due to a lack of local water sources.

Forest fires occur annually in high-risk subdistricts such as Mueang Na, Thung Khao Phuang, and Mueang Ngai due to an accumulation of dry leaves and twigs which serve as ideal kindling.

However, steep cliffs have hampered accessibility to the affected areas, slowing down firefighting missions.

GISTDA reported 299 hotspots in Chiang Mai from March 22 to 28, with 92 erupting on Tuesday.

Northern Thailand has been grappling with numerous forest fires in recent weeks. The flare-ups are believed to be caused by the spread of agricultural burning, as farmers cheaply clear their land by setting ablaze waste crops.

It has led to soaring levels of harmful PM2.5 particles in the atmosphere, with air pollution in Chiang Mai and Chiang Rai the worst in the world this week.