Delhi: Air quality in the Indian capital deteriorated to a severe level, prompting authorities to initiate anti-pollution measures and advise vulnerable populations to remain indoors.

According to Anadolu Agency, the air quality index in Delhi reached a critical score of 491 out of 500 on Sunday morning, as reported by the Central Pollution Control Board. This marked an increase from Saturday's evening reading of 441, underscoring the escalating pollution crisis in the city.

In response to the severe pollution levels, the Commission for Air Quality Management activated Stage IV of the Graded Response Action Plan on Saturday. This is the highest level of action in the plan, as per a statement from India's Environment, Forest and Climate Change Ministry. The plan includes restrictions on the entry of older diesel trucks, a halt on construction activities including public projects, and the implementation of hybrid schooling to limit outdoor exposure.

Authorities have strongly advised residents, especially children and individuals with respiratory or heart conditions, to stay indoors and wear masks if they need to go outside. The deteriorating air quality has been attributed to high humidity and a shift in wind direction, which hinder the dispersion of pollutants and contribute to the formation of smog.