Thick smog causes health warnings in Beijing

16 January 2014 Last updated at 17:12 GMT

Severe smog has hit the Chinese capital, Beijing, and officials have advised children and older people to stay indoors, as air pollution hits dangerous levels.
Tiananmen Square in Beijing is shrouded with heavy smog
Severe smog has hit the Chinese capital, Beijing, and officials have advised children and older people to stay indoors, as air pollution hits dangerous levels.
Tiananmen Square in Beijing is shrouded with heavy smog
Readings on Thursday registered more than 20 times the recommended exposure levels by the World Health Organisation (WHO). This sign reads: "protecting atmospheric environment is everyone's responsibility".
Tiananmen Square in Beijing is shrouded with heavy smog
Thick smog reduced visibility to a few hundred metres, shrouding buildings and leaving a strong smell in the air.
A group of women wear face masks as they make their way along a street in Beijing on January 16, 2014.
Officials advised people walking to work to wear protective face masks.
A Chinese policeman stands surrounded by thick smog in Beijing
China's cities are frequently blanketed by pollution caused by coal-burning power plants, factories, and millions of vehicles on the roads, says the BBC's Martin Patience in Beijing. But this policeman stood his ground.
Smog covers a busy highway in Beijing
Four highways linking Beijing to other cities were temporarily closed on Thursday morning due to poor visibility, Xinhua news agency says. Officials have promised to do more to clean up the air.