A thick blanket of dust has enveloped large swathes of the Indian capital New Delhi, with monitoring stations recording severe levels of air pollution.
The elderly and children were advised to remain at home as the dusty conditions that set in on Tuesday night are likely to persist until Friday.
The current problem is blamed on winds which are bringing in dust from the north-western desert state of Rajasthan, Sunita Devi, a scientist from the Indian Meterological Department's forecasting centre said.
New Delhi is reeling under scorching heat of 42C and the atmospheric conditions were not allowing the dust to disperse, she added.
Concentrations of PM10, considered particularly harmful to health, ranged between 800 and 1400 micrograms per cubic metre at different places in the city compared to a safe level of 100 since Tuesday, data from monitoring stations in the city showed.
PM10 refers to inhalable particles that are generally 10 micrometres or smaller.
Local media reports carried stories about residents complaining of breathlessness, burning of eyes and irritation in the throat.
Delhi, a city with a population of 20 million, has been ranked among the worst-polluted cities in the world in recent years.
Australian Associated Press