Tehran shuts schools as thick smog is linked to hundreds of deaths

Authorities in Iranian capital forced to take emergency action amid unprecedented levels of air pollution

At this time of the year, citizens of Tehran are accustomed to a thick curtain of fog that falls across the city, veiling everything from the 435 metre-tall Milad tower to the nearby Alborz mountains.

This week, however, the blanket of smog smothering the Iranian capital has been blamed for a string of deaths and prompted unprecedented emergency measures by the city's authorities.