The National Capital of India is known to be one of the polluted cities in the World, but now two more Indian cities have joined the list among the world's worst 10 for pollution due to heavy smoke in the air a day after revellers let loose with firecrackers for Diwali.

New Delhi took, as it often does, the top spot. It had an air quality index (AQI) figure of 420, putting it the 'hazardous' category, according to Swiss group IQAir.

But it was also joined in the top 10 by Kolkata, which came in fourth with an AQI of 196, while the financial capital of Mumbai was eighth with an AQI of 163.

Air quality in India deteriorates every year ahead of winter, when cold air traps pollutants from vehicles, industry, construction dust and agricultural waste burning.

Delhi has been constantly witnessing severe and hazardous air quality days, and the conditions doesn't seem to be improving.