Smog caused by high levels of PM 2.5 air pollution covered the skyline in Bangkok, Thailand, this morning.

The haze, which is worst in winter months, is caused by a combination of agricultural burning and still atmospheric conditions.

Officials at the country's Pollution Control Department found levels of particulate matter 2.5 micrometers and less in diameter ranged from 39 to 73 microgrammes per cubic metre of air. The safe level is around 50mcg. They advised residents to stay indoors and avoid using their cars too much.

Scientists believe the country's air pollution is caused by a combination of still atmospheric conditions, agricultural burning and soaring numbers of cars and construction projects.

Researchers found that smog - caused by high levels of harmful PM 2.5 particles in the air - is at its worst in the country when farmers burn waste crops to cheaply clear their land between late October and April.

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

The Thai government has been criticised for failing to tackle the country’s air pollution crisis, which worsened in 2019 leading to large numbers of people suffering from respiratory problems.