Air quality monitors in the Indian capital reached their maximum “hazardous” level as Diwali celebrations left New Delhi engulfed in a thick layer of smog - despite a court ban on toxic fireworks.

More than 300 people were arrested in New Delhi and 200 in Kolkata for flouting a Supreme Court order that only “green firecrackers” were to be let off, and only between 8pm-10pm.

On Thursday morning the skies over Delhi were opaque from the smoke and street-level visibility had plunged to barely more than 100 metres.

Some of New Delhi’s monuments including the India Gate and Red Fort were blanketed by a noxious hue. Residents wore masks and goggles as they struggled to see properly on major roads.

The yearly smog is the combined result of millions of cheap fireworks containing sulphur and charcoal, Delhi being in a geographically low location for smoke to clear, harvest-time burning by farmers in neighbouring states and a lack of rain.