In pictures: Smoky skies in Delhi on Diwali as revellers defy firecracker ban

A toxic haze began to circulate in New Delhi on Sunday as people in the city of 20 million, which has struggled with heavy pollution recently, defied a ban on firecrackers on the night of Diwali, the annual festival of light.

Smoke plumes were visible across the sky as revellers let off firecrackers in the evening to mark the country's biggest festival.

Every year government authorities or India's Supreme Court impose bans on firecrackers - but only rarely do those bans appear to be enforced.

The Air Quality Index (AQI) across all 40 monitoring stations in the capital averaged 219 on a scale of 500, according to the federal pollution control board data, indicating "poor" conditions that can affect most people on prolonged exposure.

The AQI data also showed that the concentration of "PM2.5" poisonous particulate matter in a cubic metre of air was around 100 micrograms per cubic meter - 20 times higher than the World Health Organization's (WHO) recommended maximum.

Globally, air pollution was the worst in India's eastern city of Kolkata, while Delhi was the fifth-most polluted, according to Swiss group IQAir. Doctors say the air quality is likely to worsen on Monday as smoke from firecrackers lingers in the air, potentially causing itchy eyes and irritation in the throat.

Some resent the Diwali firecracker bans, which they see as an attempt to interfere with them observing their religious festivals.

Earlier in the day, Delhi's Environment Minister Gopal Rai had urged citizens to steer clear of firecrackers to prevent citizens from having breathing problems later.

Air pollution level is expected to soar again after the celebrations end Sunday night because of the fireworks used. Last week, officials in New Delhi shut down primary schools and banned polluting vehicles and construction work in an attempt to reduce the worst haze and smog of the season , which has posed respiratory problems for people and enveloped monuments and high-rise buildings in and around India’s capital.

Some Indian states have banned the sale of fireworks and imposed other restrictions to stem the pollution. Authorities have also urged residents to light “green crackers” that emit less pollutants than normal firecrackers. But similar bans have often been disregarded in the past.

Diwali, a national holiday across India, is celebrated by socialising and exchanging gifts with family and friends. Many light earthen oil lamps or candles, and fireworks are set off as part of the celebrations. In the evening, a special prayer is dedicated to the goddess Lakshmi, who is believed to bring luck and prosperity.