The Iranian authorities are introducing traffic restrictions in the capital, Teheran, from today Wednesday because of severe air pollution.

Drivers will only be allowed on the city's roads on alternate days - depending on whether their license plate begins with an odd or even number.

Educational centres will be closed, and old people or those with heart problems have been asked to stay indoors.

State radio said pollution was six times higher than levels set by the World Health Organisation.

Correspondents say vehicles are the main source of air pollution in Teheran with most cars more than twenty years old.