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.

India's pollution control authority said the national capital territory's 24-hour air quality index (AQI) reading was at 484, classified as "severe plus", the highest this year.

NEW DELHI (Reuters) -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.

The India Meteorological Department (IMD) issued an orange alert for November 18, forecasting dense fog and smog conditions throughout the morning, with temperatures expected to dip gradually over the next five days.