Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region, and pollution in the capital Delhi remained severe.

Toxic smog engulfed much of northern India on Monday and pollution readings in New Delhi hit their highest of this pre-winter season.

Delhi's air-quality index, or AQI, shot up past 1,000 on Monday, more than five times higher than Sarajevo, the second most-polluted major city.