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.

Record-breaking levels of thick, toxic smog that have shrouded eastern Pakistan and northern India since last month can be seen in striking satellite imagery.

With cities in India and Pakistan ranking among the world's most polluted, new technologies must be adopted to tackle dangerous levels of winter smog, environmentalists urge.

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.

Pakistan's Lahore remained the world's most polluted city, while visibility in parts of northern India fell to zero. Seasonal crop burning, low winds, and dropping temperatures contribute to toxic smog in these regions.

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

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.