Air pollution in the north of India has “reached unbearable levels,” the capital Delhi’s Chief Minister Arvid Kejriwal says.
Air quality in Delhi reached the “hazardous” category on Sunday.
Schools have been closed, more than 30 flights diverted and construction work halted as the city sits in a thick blanket of smog.
Mr Kejriwal called on the central government to provide relief and tackle the toxic pollution.
How bad is the smog?
Levels of dangerous particles in the air – known as PM2.5 – are far higher than recommended and about seven times higher than in the Chinese capital Beijing.
An Indian health ministry official said the city’s pollution monitors did not have enough digits to accurately record pollution levels, which he called a “disaster”.
Five million masks were handed out in schools on Friday as officials declared a public health emergency and Mr Kejriwal likened the city to a “gas chamber”.
How are people reacting?
Mr Kejriwal’s most recent comments are unlikely to please government officials, reports the BBC’s South Asia regional editor Jill McGivering. She said Indian politicians were blaming each other for the conditions.
On Sunday young people in Delhi came out to protest and demand action.
“You can obviously see how terrible it is and it’s actually scary you can’t see things in front of you,” said Jaivipra.
She said she wanted long-term and sustainable anti-pollution measures put in place.
“We are concerned about our futures and about our health but we are also fighting this on behalf of the children and the elderly who bear the biggest brunt of the problem here,” she said.
What’s caused the pollution?
A major factor behind the high pollution levels at this time of year is farmers in neighbouring states burning crop stubble to clear their fields.
This creates a lethal cocktail of particulate matter, carbon dioxide, nitrogen dioxide and sulphur dioxide – all worsened by fireworks set off during the Hindu festival Diwali a week ago.
Vehicle fumes, construction and industrial emissions have also contributed to the smog.