Schools in Beijing are closed and outdoor construction halted as the Chinese capital’s first ever pollution red alert come into effect.
The alert was issued on late Monday and midday on Thursday.
Limits have been placed on car use and some factories have been ordered to stop operations.
It comes as China, the world’s worst polluter, takes part in talks on carbon emissions in Paris.
It is the first time China has declared a red alert under the four-tier alert system, which was adopted a little over two years ago, although pollution levels were far from the city’s worst.
