Dense smog in Beijing China stops hundreds of flights
Beijing airport has cancelled hundreds of flights after dense smog reduced visibility in the Chinese capital.
Fog across parts of northern China meant motorways had to be closed and many drivers kept their headlights on all day.
In Beijing the fog was made worse by air pollution and the US embassy there said particulate levels were "hazardous".
Weather forecasts suggest the fog will continue until Wednesday.
Beijing airport, which is the world's second busiest by passenger traffic, cancelled more than 200 flights on Monday. Thousands of passengers were stranded.
The Chinese capital is considered to be one of the most polluted cities in the world by international organisations, including the UN.
The high level of air pollution comes from burning fossil fuels, particularly coal, and from vehicle emissions.
Motorways linking Beijing to other parts of northern China were closed for parts of Monday as heavy fog made driving conditions dangerous.