Three rescue elephants carried logs to help prevent a wildfire from spreading in northern Thailand.

The trio named Plai Valentine, Plai Saen Champ, and Phang Saen Duen, took part in firefighting efforts at a forest in Chiang Mai on March 26.

Footage shows the jumbos moving heavy tree trunks and large branches as their firemen created firebreaks to keep the inferno contained.

Phra Kru Odd, founder of a local elephant sanctuary, said: 'The elephants and their mahouts joined hands with volunteers to protect the forest and wildlife.

'Today, three elephants were sent to join the firebreak operation. They can enter the area more easily than vehicles, and can move large trees that might serve as fuel for the blaze.'

Chiang Mai in northern Thailand was among the 10 worst cities in the world for air quality, international air monitoring company IQAir reported on March 26.

The city saw up to 80 microgrammes of PM2.5 pollutant particles per cubic metre of air, which is classified as 'unhealthy for sensitive groups'. The safe levels advised by the World Health Organisation are five microgrammes.

The wildfire comes amid the country's yearly crop burning season, during which selfish farmers set fire to their fields to cheaply clear their land.

Scientists found that smog is at its worst in the country during the crop burning season in late October and April. The agricultural process known as 'slash and burn' is quicker and easier than crop rotation fields and leaves a nutrient-rich layer of ash that helps to fertilise new crops.

However, the side-effect is severe air pollution full of toxic PM2.5 particles that cause respiratory ailments. The pollution has also worsened in recent years due to the rising demand for food from rapidly developing cities in Southeast Asia.

The lack of wind and rain during the same period, combined with a winter low-pressure system in which cold air is trapped closer to the ground by warm air above, prevent the smog from being dispersed naturally by wind.

Thailand's government has been criticised for failing to tackle the country's air pollution crisis, with bizarre measures such as spraying water into the air, placing giant purifiers on roads and even using cloud-seeding planes to cause downpours. There have also been claims that they are under pressure from powerful food conglomerates to allow the intensive farming methods.

Thailand has an estimated 4,000 elephants in captivity. They are put to work in the logging industry, at tourism resorts or kept privately for use at religious events and rituals.

A number of rescued elephants also live in sanctuaries, where they can wander through enclosed land.

However, there is ongoing debate about the treatment of all captive elephants, with organisations such as People for the Ethical Treatment of Animals (PETA) calling for their release.