Cooler temperatures and lighter wind trapped heavy smog over the Indian capital on Wednesday, pushing pollution to ‘severe’ levels in many places with no immediate relief in sight, government agencies said.

Millions of people in India's capital started the week Monday choking through "eye-burning" smog, with schools closed, cars taken off the road and construction halted.

Pollution in the Indian capital, New Delhi, rose to a ‘severe’ level on Thursday after revellers let off fireworks long into the night to mark the Hindu festival of Diwali.

India may halt the use of private vehicles in the capital New Delhi if air pollution, which has reached severe levels in recent days, gets worse, a senior environmental official said on Tuesday.

India on Wednesday unveiled a new weapon against air pollution -- an ‘anti-smog gun’ which authorities hope will clear the skies above New Delhi but which environmentalists say amounts to a band-aid solution.

India's second innings was into its sixth over when Lakmal was seen bending over and throwing up. The Sri Lankan physio rushed in and eventually walked off with the player.

Many of Sri Lanka's fielders returned from lunch on the second day of the Test against India wearing masks amid visible haze at the Feroz Shah Kotla stadium.

A thick cloud of toxic smog 10 times the recommended limit enveloped India's capital New Delhi on Monday, as government officials struggled to tackle a public health crisis that is well into its second week.

In the emergency ward of a Delhi hospital, men and women gasp for breath as they wait to be treated for symptoms triggered by the choking blanket of smog that descended on the Indian capital this week.

Illegal crop burning in farm states surrounding New Delhi, vehicle exhaust in a city with limited public transport and swirling construction dust have caused the crisis, as they do year after year.

Schools closed across large swathes of north India on Thursday as pollution hit hazardous levels for the third day, with growing calls for urgent government action to tackle what doctors are calling a public health emergency.

A thick brown smog hung over Delhi with residents reporting smarting in the eyes and irritation in the nose and throat.