Air pollution choking New Delhi has ground outdoor work to a halt and disrupted air travel in the Indian capital.

India's government banned non-essential construction in New Delhi, the world's most polluted capital, and urged residents to avoid burning coal for heating, to combat worsening air quality that has disrupted flights and obscured the Taj Mahal.

A dense smog blanketed the Taj Mahal in Agra on Thursday as pollution levels surged, obscuring the iconic monument from view. Tourists captured visuals showing the Taj Mahal nearly invisible behind the haze.

Northern India encountered the recurring annual pre-winter event of air emergency where the Air Quality Index (AQI) readings of main pollutant PM 2.5 breached the 400-mark of “very poor” and landed the air of Delhi, Punjab and other northern cities into the “hazardous” category.

Delhi's air quality turned 'severe' for the first time this season on Wednesday, with the AQI soaring to 418. In comparison, the national capital's 24-hour average Air Quality Index (AQI) -- recorded at 4 pm every day -- stood at 334 on Tuesday.