NEW DELHI- New Delhi, on Friday, awoke to a thick, hazardous haze that forced the closure of some schools for two days due to the air quality index (AQI) reaching "severe" levels in various parts of the city.

The annual winter smog, caused by cold, stagnant air trapping construction dust, vehicle emissions, and crop stubble burning smoke from neighboring states, has once again gripped the Indian capital, leading to a rise in respiratory illnesses among its 20 million residents.

Complaints of eye irritation and itchy throats were widespread as the AQI hovered around 480 at certain monitoring stations, far above the safe range. An AQI of 0-50 is considered good, while levels between 400-500 are harmful to both healthy individuals and those with preexisting conditions.

New Delhi claimed the unenviable top spot on a real-time list of the world's most polluted cities on Friday, with an AQI of 611, classified as "hazardous" by the Swiss group IQAir.

Unfavorable weather conditions, a sudden increase in agricultural fires, and winds carrying pollutants from the north-west were identified as the primary causes for this alarming AQI spike by the region's Commission for Air Quality Management.

To combat the crisis, authorities mandated the closure of primary schools on both Friday and Saturday, and most construction activities were put on hold. The surge in demand for air purifier filters in the region left some suppliers struggling with shortages.

The deteriorating air quality has cast a shadow over India's hosting of the cricket World Cup, with Mumbai also experiencing a sharp increase in pollution levels. Delhi is set to host a World Cup match on Monday between Bangladesh and Sri Lanka.

In the previous year, Bhiwadi in northern India held the dubious title of the country's most polluted city and was ranked third globally by IQAir. New Delhi came in fourth, while Lahore in Pakistan and Hotan in China claimed the top spots on the list of the world's most polluted cities.