Toxic smog in India and Pakistan has caused air quality in the major metropolitans of Lahore, Multan, Delhi and Chandigarh to deteriorate to toxic levels.

Pakistan's Lahore remained the world's most polluted city, while visibility in parts of northern India fell to zero. In India, the smog was so thick it caused flight delays and blocked views of the Taj Mahal,

Pakistan’s cities slip under toxic smog as live readings for Lahore show PM2.5 levels 100 times over what WHO prescribes

The government in Lahore has closed schools and public spaces and shut down factories. Environmental lawyer Ahmad Rafay Alam shares his perspective: "frustrated" but still fighting.

The satellite images show an extremely heavy grey smog over Pakistan. It stretches into northern parts of India, albeit is lighter than the one over its neighbouring country.