An emergency measure banning half of Delhi’s private vehicles from the road was introduced on Monday to combat the city's air pollution, which has risen to more than 20 times the safe limit.

As smog levels grew - making it three times worse than in Beijing - authorities also parked a van with an air purifier near the Taj Mahal 250 kilometres (150 miles) away in a bid to clean the surrounding air.

The level of particulates measuring less than 2.5 microns was over 700 micrograms per cubic metre of air on Monday morning, according to the Air Quality Index (AQI).

The World Health Organisation's safe daily maximum is just 25.

Health officials have instructed Delhi’s 29-million population to stay inside as a reading of over 500 can cause serious aggravation of heart and lung diseases.

The BLK Hospital reported a 300 per cent increase in admissions from respiratory problems since Saturday, with children suffering particularly badly with the toxic air.