New Delhi, Nov. 7 -- Air pollution levels in Delhi surged by more than 100 points on the air quality index (AQI) on Thursday, as smoke from farm fires in Punjab and the bursting of firecrackers overnight in the capital, combined with local emissions trapped by calm winds and falling temperatures, shrouded the city in a thick haze.

The AQI stood at 311 in the "very poor" category at 4 pm, up from 202 a day earlier, when people in several parts of the city illegally burst firecrackers to celebrate Gurpurab.

The grey haze that descended late on Wednesday persisted through Thursday morning, a stark contrast to the visually cleaner blue sky just a day earlier, as pollution made eyes water, throats scratchy and skin itchy.

Stubble burning in...