GRAP stage 3 will come into force at 8am on Friday. The Delhi government announced that classes for primary schools will be shifted to online.

Delhi air quality plummets to alarming levels every year in the winter. The air quality in the capital remains in the 'severe' category prompting the authorities to impose the third stage of GRAP.

In a repeat of what occurs every year, Delhi is engulfed by toxic smog as air quality remained in the "severe" category at the onset of winter in the national capital, media reports said.