Air quality in India's capital New Delhi deteriorated to hazardous levels on Tuesday, recording the world's highest pollution levels, according to Swiss monitoring group IQAir.

The spike followed widespread firecracker use during Diwali, the Hindu festival of lights. Iconic landmarks such as the India Gate and Akshardham Temple were shrouded in thick smog, with hazy skies across the city. IQAir measured New Delhi's air quality index at 442, with PM2.5 levels more than 59 times above the World Health Organization's recommended annual guideline.