Panic gripped the Indian capital Delhi on Monday (Nov 5) as residents woke up to a blanket of thick grey smog ahead of Diwali, the festival of lights.
Visibility is poor as pollution levels reached 20 times the World Health Organisation's recommended limit.
The air quality is expected to worsen in the coming days due to the use of firecrackers, experts have warned.
Indian cities regularly dominate global pollution rankings for the worst air quality.
The Supreme Court has restricted the timeframe for setting off firecrackers to only two hours during the day - but experts believe this curfew will be hard to implement.
Diwali, the most important Hindu festival in north India, celebrates the victory of good over evil.
However in the last few years, celebrations have seen air pollution rise to hazardous levels after many firecrackers were set off.
Many have taken to social media to share their concerns as well as post dramatic photos of the city to show the extent of the problem.
- Source: BBC News