Reports say that more than a hundred workers at a metallurgic plant in the Urals region about 1,500km east of Moscow have been taken ill following an escape of toxic fumes.

Russian television said that an electrical failure had set off a chemical reaction and a workshop was filled with nitric acid vapor.

At least four workers were reported to be in critical condition and many others are said to be suffering from burns to their respiratory systems.

From the newsroom of the BBC World Service