In pictures: Smog hits Beijing

A woman wearing a mask makes her way amid the heavy haze in Beijing on 23 February 2014

Air pollution has shrouded parts of northeast China since Friday, leaving residents choking on hazardous levels of smog.

Residents stretch their legs during morning exercises on the top of Jingshan Park near the Forbidden City on a hazy day in Beijing on 21 February 2014

Particulate readings in Beijing soared to 15 times WHO-recommended safe limits on Friday - reaching "orange" levels, the second-highest possible.

A smog hangs over the business area on 23 February 2014 in Hangzhou, China

The smog has persisted through the weekend, shrouding other Chinese cities including Hangzhou.

A man wearing a mask rides a bicycle in Beijing 24 February 2014

By Monday the alert level was down to "yellow", but many residents wore protective masks as they went about their daily lives.

Visitors are silhouetted against thick smog on the top of Jingshan Park near the Forbidden City in Beijing on 24 February 2014

In response, the Beijing government has ordered checks on construction work and polluting industries, and banned open-air barbecues in the city.

A man and his dog, both wearing masks, walk along a small alley on a hazy day in Beijing on 23 February 2014

Residents have lived with the pollution for several years - and it tends to get worse in winter.

Children with respiratory illness receive treatment at a hospital in Beijing on 21 February 2014

High levels of smog can be harmful to health, the WHO has warned, causing respiratory illness in vulnerable people.