An unprecedented dust storm engulfed Iran's capital Tehran on Monday, having
entered the western and southwestern parts of the country a few days ago.

The dust has created poor visibility, rendering Tehran's nearby Alborz
Mountains and its 435-metre Milad tower disappear from the sight, and many
domestic flights have been cancelled.

The blowing sand is also adversely affecting air quality, and local health
authorities were giving out free masks to residents.

Authorities urged residents with heart and respiratory diseases to remain
indoors.

The dust, which is thought to originate in the deserts of Iraq, had already
hit other big cities in Iran such as Ahvaz and Kermanshah.

The dust storm was expected to blow over by Tuesday.