Air pollution and a high volume of dust particles have led to the closure of schools and government offices in Zabol.
IRNA reports that according to Zabol Governor Hooshang Nazeri, the level of air pollutants in the city in recent days has been 40 times acceptable world standards and 12 times over dangerous levels.
The Zabol weather office puts visibility at less than 50 metres around the airport.
Environmental experts cite the drying of wetlands as one of the chief reasons for rising dust volumes in the region.